James, you can also get it from Mac's Products. They charge an arm and a leg for it though. Look in the phone book for metal supply houses. We have one around here that sells nice aluminum tubing cheaply. It is not quite as thinwalled as the Mac's stuff though but will work nicely and comes in all sizes.

Usually 1" header pipe is used on 46 size engines, and 3/4" on the 25 - 32 size I think though....

Do you have a link to that SPAD site you mentioned? I would like to see the mousse can info there.

Ernie