CR480 engine in a '81 250 frame

[JohnnyO]

I'm thinking it will fit because the '81 250 and 450 had the same shape crank cases and the 480 is basically a bored out 450. Without the radiators on the 250 frame there shouldn't be any clearance problems

[GT43]

If you are building a bitsa all the major oem components have to be from evo bikes. Better grab a rule book

I gather that it is OK to use cosmetics from a Pre-85 onto an Evo bike? 
As have seen a few "YZ-J" Tanks / seats on "H" models.