Schmaucher creative services have the swap mounts and headers for this swap, though there not race headers. There covered by Hooker IIRC and Headman Headers as well as tti.
The only fabing needed in his "74" would be the motor mount to install the engine. I used regular headman header for a B body in the A body without much issue at all, though a buddy is key for ease of things. Everything else would be the same for a small block.
While I'm a small block fan, er, nut(case), I did want to do this for a long time.
IMO, the only real expense over building a stock stroke 400 over a small block is the price of slugs and fender wall headers with minor price increases with parts normally seen as more with big blocks. A few bucks for heads, a few bucks for this, that, etc......
I'm slowly doing a 400 in a 71 Duster now. It'll stay a stock stoke 400 for awhile.