You might want to try
http://www.inetworld.net/~brattlan/
I'm running 3/2 Holleys on my 302 (347 stroker). I bought'em used and bought this guy's manual to set them up. There is also a classified page at his site... you should be able to get a manifold there.
He is Mike Brattlan, knows his stuff about tri-powers
- Dan