72 4wd getting a big block

[Agent]

Hello, I am new to this site and was wondering if anyone had any advice for installing a 402 BB in my 72 4wd Cheyenne? I have set a dummy block in place with the small block motor mounts and it seems to bolt up ok. I have heard that if you use the small block engine "perches" that I may have exhaust issues. I plan on using headers but don't have any at the moment to try.

Any thoughts or advice would be appreciated. Thanks