Well, the fast-for-cheap options always seem to dry up pretty quickly. The Camaro is a good choice - decent aero, easy to work on and cheap-as-dirt go-fast parts, but that cat's been skinned so may times, all that's left is the carcass.
But you add that word "competitive", and all of a sudden, ski boats and race horses are looking like affordable hobbies.
Good luck on this. It helps enormously to have ones spouse on board. You and I are both fortunate on that front.