A Gasser was actually a car that fit in the "Gas" class of drag racing. While I'm sure you can find the specifics for the class waaaay back when, basically "Gassers" were cars tha had modified suspensions beyond factory, allowed for engine swaps from makes other than the car body (I.E. Chevy body/Mopar engine) , had an interior & were based on a lbs/cu.in basis (I think). These are not to be confused with Altereds or the Modified Production classes of the era that, although similiar in appearence in some cases, were a completely different class of car with their own requirements.