Williamson breaks Fleming's record for most 50-plus Test scores.
The selectors have also put Bilal Asif, Imran Butt, Musa Khan and Mohammad Nawaz on standby to cover for any player who fails pre-tour COVID-19 Testing scheduled later this month.
Leg-spinner Yasir Shah marks his return to the national men's team as Pakistan on Wednesday announced an 18-member squad for next month's two-match Test series against Sri Lanka.
Pakistan had been reduced to 76 for five in their second innings as South Africa's spinners made inroads through the top order having been bowled out for 201 in another shambolic display with the bat.
The win also pushed the Black Caps firmly into contention for one of two berths in June's inaugural World Test Championship final at Lord's.
Six of the 10 Pakistan cricketers bound for England who tested positive for COVID-19 have now registered negative results on re-testing, the Pakistan Cricket Board (PCB) said on Saturday. Mohammad Hasnain, Shadab Khan, Fakhar Zaman, Mohammad Rizwan, Mohammad Hafeez and Wahab Riaz, however, must return a second negative result before they can join the main squad of 20 players who will leave for England on Sunday.
Fast bowler Dwaine Pretorius took a record 5-17 in South Africa's six-wicket victory.
For South Africa, Rassie van der Dussen has advanced three slots to the sixth position, just one shy of his career-best, after scores of 34 not out and 52.
Jacques Kallis, Hashim Amla, Graeme Smith, AB de Villiers, Gary Kirsten, Herschelle Gibbs, Mark Boucher, Daryl Cullinan, and Faf Du Plessis are the other Proteas batsmen who have more than 4000 runs in Test cricket.
Devon Conway's struck 63 to help the hosts score 173/7 in their 20 overs.
The trio will replace Faheem Ashraf, Junaid Khan and Abid Ali after selectors spoke with skipper Sarfaraz Ahmed and coach Mickey Arthur following Pakistan's 4-0 defeat by England in their recent ODI series.
Electing to bat, Hong Kong folded for a paltry 116 in 37.1 overs, courtesy Usman's 3 for 19 and two-wicket hauls by Shadab Khan (2/31) and Hasan Ali (2/19).
KL Rahul retained his third position, while India captain Virat Kohli improved a rung to the seventh spot in the ICC men's T20I Batting Rankings.
Captain Aaron Finch scored a century as Australia beat Pakistan by eight wickets in the opening One-Day International between the countries at the Sharjah Cricket Stadium on Friday. Chasing 281 to win, the tourists reached their target with an over to spare and took a 1-0 lead in the five-match series, with Finch making 116 and Shaun Marsh unbeaten on 91.
Pakistan have dropped out-of-sorts pace bowler Mohammad Amir from their 17-man squad for next month's two-Test series against Australia in the United Arab Emirates, with left-arm seamer Wahab Riaz earning a recall.
Arthur described coaching the Pakistan team as a fulfilling period of his career.
End of chopping and changing has brought stability to white ball tea, says Pakistan captain Sarfraz
Pakistan will be eager to raise their game.
South Africa's fiery seamer Duanne Olivier took five wickets as the hosts powered into the ascendancy on day two of the third and final Test against an outgunned Pakistan at the Wanderers on Saturday.
Pakistan dominated the first day of the opening Test after bowling out England for 184 and battling to 50 for one in overcast conditions at Lord's in London on Thursday.
Pakistan resumed their second innings needing a further 228 for victory with seven wickets in hand, but their chances faded when Olivier removed the dangerous Babar Azam (21) and captain Sarfraz Ahmed (0) in consecutive balls.
The PCB banned Shehzad for violating anti-doping regulations after he tested positive for a prohibited substance in May and his suspension was scheduled to end on November 10.
IMAGES from Day 2 of the 1st Test between England and Pakistan at Lord's on Day 2
West Indies and Bangladesh will play two Twenty20 matches in Florida in August, Cricket West Indies (CWI) announced on Tuesday.
Deepak Chahar is the first Indian bowler ever to hold the record of best bowling figures in any format of international cricket (Test/ODI/T20I), points out Rajneesh Gupta.
If Australia win all four Tests against India, and South Africa beat Pakistan 3-0, then South Africa will take over the No. 1 spot, ahead of Australia by a fraction of a point.
England made a bright start to their second Test against Pakistan at Headingley on Friday, after being hammered at Lord's last week, with Stuart Broad taking two early wickets and the visitors reduced to 68-4 at lunchtime.
India are eyeing a place in the final after three wins in as many matches, while Pakistan will look to step up their game in the Super Four match, after a scare against Afghanistan.
England have by far been the best team in the tournament.
Both the teams lost their opening matches but bounced back into reckoning after producing two of the tournament's biggest upsets so far.
Uncapped left-arm spinner Zafar Gohar has joined the test squad from the Pakistan A team currently in Hamilton.
Bhuvneshwar Kumar and Kedar Jadhav claimed three wickets each followed by Rohit Sharma's quickfire half-century as India registered a comprehensive eight-wicket victory against Pakistan.
Rohit Sharma-led India's main aim would be to settle their middle-order combination and also find a perfect batting position for Mahendra Singh Dhoni.
The 16-man squad includes batsmen Mark Stoneman and Dawid Malan and fast bowler Jake Ball, who have 11 Test caps between them, as well as three uncapped players in paceman Craig Overton, spinner Mason Crane and wicketkeeper Ben Foakes.
England, who have won both the one-day and Twenty20 series against Sri Lanka, play a two-day practice match in Colombo before heading to Galle which hosts the first of the three Test matches from November 6.
India, along with the mighty Australia, will start as title contenders in the ICC Champions Trophy.
One of the finest fast bowlers in current times, Mohammed Amir would be pitted against the talismanic Virat Kohli in what could turn out to be a battle primarily between India's vaunted batting line-up and against Pakistan's potent bowling attack.