Which 8 HP engine? Got some pics or the nomenclature?
If it is an 8HP flathead, I don't think there's much in the way of performance parts for the 8 HP, but any carburetor that you can bolt up should work.
Just try to match the bore size of the old one or in other words make sure it is large enough to deliver the fuel/air volume that an
8 horse needs. You can connect basically any carb if you have the proper intake manifold.