What if LBJ hadn't forced out Tom Clark? LBJ OTL made Ramsey Clark AG on the assumption that he was a moderate conservative with liberal-populist tendencies like his father had been. He was less than pleased to learn that Ramsey Clark was fairly inclined towards the New Left. Tom Clark stepped down to facilitate his son getting the AG position. But LBJ later said that if he'd known Ramsey's actual views, he'd never had made Ramsey AG.
There would be a few consequences.
First, Thurgood Marshall would not have been elevated to the Supreme Court and remained Solicitor General. What he does afterward, I'm not sure. Maybe he returns to private practice and continues to make change there.
Second, LBJ has more political capital when replacing Earl Warren. OTL more than a few southerners muttered to him that they already voted for a "n*****" and couldn't be expected to elevate a Jew (Fortas). Maybe Fortas would fail either way, I'm not sure. And also, maybe Marshall is nominated to replace Fortas instead of Thornberry (I'm not sure).
Third, you have Clark on the bench instead of Marshall. In some cases, like Katz, this might make a difference since Marshall recused himself. Maybe a beefier Fourth Amendment standard than we got historically.
Fourth, Clark was the only Justice to join Griswold in full and later wrote a paper on the abortion issue before Roe. His presence on the Court may moderate things down the line, avoiding social tension in Roe. He may be part of the bloc that votes to resolve the case in 1972. His view seemed to be closer to adopting the AMA's position - that 'ratification' of longstanding de facto legal abortions was a positive reform.
Fifth, Clark probably retires before 1973 (thus under Nixon, or whatever other Republican is running things). You would have another moderate-to-conservative Justice instead of Thurgood Marshall. If Nixon wants to try for the First African-American Justice, the likely option would be William T Coleman. But Nixon being Nixon, he might just not care at all.