Sorry Dave...there was a thread here awhile ago that had a link to some VERY comprehensive info on gassers...right down to breakdowns of all the classes. If I remember correctly, they were largely pounds per cubic inch classes. In the early days, I'm assuming for weight and simplicity reasons, to get the frontend up for better weight transfer, straightaxles were common. By the most technical definition, to really be a gasser one would have to be racing in a gasser class...say, for instance, my 56 Plodge weighs 3600# and is 360 CI. 10#/CI. That would put me in (theoretically, as I don't remember the numbers) B/Gas. If I was supercharged, I think they called that SB/Gas, or something like that. The rules also required (though they did evolve over the years) things like a stock front seat, or door panels, or gas tank in a certain location, etc. Man, I really wish I'd saved the link...

That should give you a basic idea, at least.