Firstly, lower the filibuster to 60 after his 1964 landslide to make sure his most progressive legislation get passed, so he passes his desired programs, maybe even universal health care or the Taft-Hartley repeal. Imagine the reforms he could have made with that 68-32 filibuster-proof supermajority if the cloture requirement was reduced to 60.
Secondly, have him avoid escalating the Vietnam War or just limit it to a manageable level, so many funds will be diverted to his Great Society programs instead. And institute mandatory drug rehab and guaranteed minimum income (GMI) to save money.
You hit the nail right on the head Nightingale
with your comment on Vietnam. Let me
just add that LBJ would have had to, some-
way, somehow, prevented the inner-city
riots of 1965-67. They gave all too many
white people the impression the country was
in chaos, a state of affairs that was blamed on all the $ that was being spent on LBJ's
Great Society programs. They thus were all
ears when Conservatives called for its ending.