realistically, I think you need 650hp to be somewhat competitive, most of the cars (at least at SEMA) have power adders or have professionally built NA race engines
I just had a look at the results from the USCA Vegas race this past week end and some of the cars, there is a lot of fast cars in the field. Even if it is an invite race you would still need to have something that was well dialed in just to qualify, I would say if I was trying to make the field that it would be easier in a newer car. Although a few old Mopars did make it in, looks like a 64 Valiant and a 69 Charger.
