A company called spitfire used to make them...good luck finding any info on them though. Dougs headers makes some, but they are of the fenderwell variety.

I believe a company called patriot makes some shorty tri y's for trucks they may work in your application as well...don't know if anyone has tried to make it work, but shorties are generally pretty forgiving...

if i could find a picture of the patriot header, I could give you an idea if it would work or at least be modified to work as I have put shorties in a 66 A body before...