I'd go for the 400ci to....bigger is always better when it comes to displacement....

I recently did an 86 Elcomino with a 400 and a 700r4 with 373 rear gears

The engine made 425 hp and 485ft tq and still knocks down 22-24mpg when your not in it.....

this was with a 216 dur@.050 comp cam and Edelbrock 2x4 intake and 2 600cfm edelbrock carbs rejetted 1 step leaner...

1st, 2nd and most of 3rd are useless but if I could get it to hook i'd bet 11's wouldn't be out of reach...