It's a production carb manifold, not custom. I thought I knew who made it, but I don't see it in their catalog. Some sidedraft ITBs will fit on it. Here it is this type of manifold assembled.
I have the same setup in a box somewhere that Rage hooked me up with.
If you need short parts for it, Kameari can sort you out.
http://www.kameariengineworks.co.jp/Cat ... 62-5-2.pdf
Here's their stateside contact.
http://www.kameariusa.com/contact/
That's who I thought made it because they have a ton of manifolds in stock.
http://www.kameariengineworks.co.jp/Cat ... -063-2.pdf
For ITBs, hit up TWM and pick up a set of 45s.
http://www.borlainduction.com/2900-series.html
Anything bigger and it would be a b**** in town, but scream on the highway.
PM Rage, too, if you use it. I think he is still sitting on a header or two. If not, I think I can scare one up.
Expect to have to hack it up and reweld it, though, to get around the steering shaft if your car is LHD.