http://www.zenithfuelsystems.com/dealers.htm
Here's the dealer locator. You'll be looking for the model 28. And then from there will be proper clocking and jetting. I purchased one of these new ones many years ago and it came with the adjustable main jet and obviously worked perfectly right out of the box. Andy (Slimsix) may be able to help with a bit of a discount but that's obviously up to him.