So you want 2 go Big block...Read this first!

It's about the same cost to swap in a small block where a slant six was originally... ask me how I know! ;)

Your exhaust quote seems really low to me. When I had the full 2 1/2 duals custom bent and installed for the 360 in my car, the bill went to $840 including the mufflers (cash, no bill). All the other quotes I got were closer to $1K to do the job.