I got a Max 1080 in the mail, put it on and it is too tight. So today I call Dennis Kirk and a talk to one of their techs. He tells me that they are listing a 1080 for my sled and he can't even find reference to a 1078 in his system. Instead of trying to help me out by taking the measurements that I needed and trying to find me a belt he got very rude and said that the Max 1080 was the only belt he could offer.
A Max 1080 that Dennis Kirk lists for the Sportfire is 46-3/16" long, the proper belt for a 1980 Sportfire is a 1078 which is 46-11/16" long.
Needless to say I am sending the belt back and will be fighting the restocking fee and I ordered one locally for a similar price but a longer wait (which doesn't seen to matter much)
Hope this will help any of you having troubles getting the right belt for your sled!
Also I have a PDF document listing belts for vintage snowmobiles that Ultimax put out if anyone is interested.