Cr500 in 2nd gen cr250r frame?

i have a 2000 cr250r and a 86 cr500, the 500 runs like a dape so i want to put it in my ally 250 frame, i know it wont bolt in as is but i have access to a tig welder at my vocational school so i was gona bring in the frame, engine and exhaust and fit it up, (havent test fitted it yet) i was wondering how hard it would b to make the swap. i look all over google and **** and i cant seem to fine any forms on fitting a 500 engine in a 2nd gen frame. my main concern is were the engine is bolted throw the swing arm bolt, idk if it will fit properly, so basically would it fit and how much work would it b to do that? please no living room mechanics