Which club are you with, Chunder?
I 'mechanic' for a guy running a 1380cc Mini in class 5 at Concord Autograss in Chelmsford.
We can't compete with mid-engined Novas (class 5 - up to 1420cc front or rear wheel drive!) but we are regularly the fastest mini-powered Mini.
I agree to a degree about what you're saying: there will always be someone ready to try and win with their wallet, but I defy anyone to spend a fortune in class 1. All you can do is have all new parts, correctly set-up as you say. Cheat and it will be obvious! If it isn't obvious, why bother!!
We have a guy running a pair of Kawasaki engines in the back of a Citroen AX. A mental motor! He didn't have linked output shafts (he does now!) and season before last, suffered a misfire on the 'inner' engine, and nearly took out the start marshall post!
Overall though, Autograss modified classes are just about the last chance for an ingenious engineer to shine.
And the best bit, you can race on beer money.