A Range Rover race car? It would go faster rolling end over end after going round a corner than it would in a straight line lol.
Being a 308, a good flowing exhaust, extractors, VN (EFI) heads and a decent carb would wake it up a bit. That can all be had cheaply.
If you want anymore after that you need to start looking at more camshaft and compression and that starts to get expensive.