The 400 tranny is going to be longer than the 350, so you won't be able to just "drop it in". Just a heads up...
wahtchoo talkin bout willis? there are 4 different tailshaft lengths avalible on both transmissions. and for the most part, where one lives, the other will too. driveshaft is the only difference.
if I dont put the 4 spd in it Im going to always wish I did, so might as well do it right the first time.
Everyone is telling you the good news about the 455 Olds, but there are some draw backs. The rocker arm support bridges break if you push RPMs and are the weak link with big cams. You are also money ahead to put a good HV oil pump in it from the beginning. They are awesome motors! I had 455 Olds in my high school firebird and no one could touch me! It was a blast and punching it at anything under 50MPH cause the back tires to lite up like John Force!!!!
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