So I purchased a used Supernova today (guess what, it doesn't rattle!). It came with a Jellyhead choke in it. I thought, great, that will save me some dough. After I got home I discovered it was labeled for a SBEII... They had been using it, it fit fine as far as threading and internally. The difference between the choke I have and the correct choke seems to be the SBEII choke is extended. There is a straight, non-threaded "extension" between the threads and the ported section that the correct choke doesn't have.
The diameter is also different. The correct choke for a Supernova is .655 and the choke I have is .660.
I'll probably pattern it and see how it goes. I was just wondering your guys' thoughts on it.