I'm just about to order a header from the states but I've seen a few cheap (soem really cheap) original bike headers and I wondered how easy it is to use one as a basis to start off?

Perhaps worth mentioning my welding skills are zip all!!

It's perfectly possible, but whether it suits your car or not is down to personal preference....
Rescued attachment 151_5114sml.jpg

That's upsidedown silly!! Put it the right way up and get some wheels off a 4x4. She'll be reet!

I bought a lovely set of titanium headers for my Indy, but just couldn't get them to fit. I think, if I'd had the exhausts and the engine when I sent it to MK to weld the chassis up they may have been able to rotate the engine slightly, and make it fit.

The only way I could see of making them fit would have been to cut a section out of the chassis and weld up some plates. And that was too big a compromise!

Sold the headers on ebay and they paid for AAS to make a bespoke manifold.

Mike