I'm fixing to stroke my 351 to a 408 but I'm trying to keep the block on pump gas. Whats the most I can go on compression? Is it better to just buy a crankkit orbuys the parts individually?

 

Depends on the chamber size of the head you will be using, but figuring a typical 58-60cc head and a dish around 22cc's will leave you around 10.5:1 depending on deck height and head gasket used. For ease, keep it at 10.5 or lower. Buy a kit as you wont know which crank will or will not use a 6.200 rod or a 6.250 rod or even a 6.125 rod and which piston will accomodate as well. Keep it simple, this is the whole point behind kits, they still need to be put together by a competent engine builder, these are not lego were playing with although people hear "kit" and think johnny and a bunch of sockets can wing it, till it blows up.