Fast
Go buy a 68-70 Cadillac Deville (sedans are real cheap, coupes next, then convertibles pull the most money). They came with 472's that with monster HP/ Torque (only the big block Vette had more those years). They burn rubber down the block and you can cram 6-8 people in it at once. You will have more fun with a Caddy than trying to restore/mod a Firebird. You won't get all the Smokey and the Bandit jokes either.
Caddys can also be found in better shape than most unrestored hot rods.
My neighbor inherited one from his grandpa and the car was tons of fun. The only catch was in FL the rust caught up with the body in less than 5 years. He intended to put the motor in a 90's pickup but let the car die in a boneyard......