what would I need to do in order to put a crank from a 96 ci into a 88 ci crank case

 

Welcome to the forum.
You're in the exhaust section and your question has nothing to do with exhaust. Try posting in the engine mechanical area, or better yet, in whichever section your type of bike is.

 

Bwahahaha....

 

it isn't the crank per say, the top end needs to match up