does anybody know if a 454 bolts into a g10 with a 305 in it, also does the dog house work or need to be modified? i dont know if id want tall or short valve covers? might roller so ill need tall thanks for any info

There are a couple threads here on Vannin.com about the bigblock swaps in GM vans.
A bigblock will drop right into your 83. No mods needed to the dog house. Stock short valve covers will work. Taller ones will not work on the drivers side without some sheet metal trimming.