New to this site. Hello all. Exhaust Question

[Toby Hines]

I am new on here and there seems to be a great deal of info on here. I have a Mid seventies P-15 GMC 1/2 ton ( same as a Chevy P-10) 102 inch wheel base Stepvan with a olson body. I removed the worn 292/Sm465 and installed a fresh 350 and th400 and I used exhaust manifolds for a 67-72 pickup, ramhorns with outlets pointing at 45 rearward. The local muffler shop wants waaaay to much to make up two head pipes. The question is, is there a company that sells or does someone have some head pipes to fit stock manifolds for a dual exhaust on a 67-72? The 73 and up manifolds are different. I think the manifolds I have will only accept 2 or 2-1/4 pipes. The engine has a r/v cam and preformer intake and carb, no hotrod just a tower and crusier.