There are a lot of crown Vics and a few Caprices running Lemons, they make very competitive Class B cars and can creep into A class. '
The biggest consideration is the consumables.
A big car going fast, stopping and turning corners is tough on tires, brakes, transmissions and fuel consumption so your weekend will cost more that a smaller car but on the flip side it is a blast to see a huge American V8 passing Hondas and Miatas.
LS engines do swap into almost anything RWD with a little fab and creativity so that is another option but maybe a bit ambitious for a first build.
Apocalyptic Racing - Occupy Pit Lane racing
Racing the "Toylet" Toyota Celica powered by Chevrolet Ecotec.
16x Loser with the Celica. 5 times loser in other fine machines