Need a bit of advice on easiest rearend swap to do on a 66 6cyl going to a 351 out of a ford lighting and I dont guess the stock rearend is going to hold up .
You will probably need a nine inch ,don't think an 8 will hold up .
67 -70 will bolt right in place but it is an inch wider on each side .
Currie can make one the correct width . I usually cut my own housing ,i have a jig .The eight inch axles from the 65-66 will work ,if you use the 4V axles.
the first question i have is how much power are you going to make from the 351? if you keep it stock then the stock six cylinder rear end will hold up, unless you are going to run slicks.
if you make less than 400hp on street tires, an 8" rear end will do nicely.
if you are going to run slicks, and/or make more than 400hp, then a 9 inch is the way to go.
an 8.8 could be used, but it would need to be narrowed, and depending on where you got the 8.8 from, the suspension mounting points would also have to be changed.