If your last build used an F20, then maybe stay with something you know?
I wonder what your hillclimbs will be like. I managed a 1st place at the Reading Hillclimb back when people still used actual stopwatches...
I also had a couple of FTD's in Vermont. In that later case I would be very cautious with a turbo or getting over powered. Driving my car on the straights was like walking on eggshells. It was around 100 MPH on a road with a 15 MPH speed limit and extensive frost heaving. The car was airborne so much of the time because of the rough pavement that it was weaving a bit.
My formula ford only has 106 HP and about 1100 lbs. With a lot of power and especially turbo lag there could be an unhappy result.
Here's a video of someone that had a 200+ HP Caterham I think. It's an old video but really well made, I think he had a job in film production. There are some other videos he made too.
https://www.youtube.com/watch?v=ntsNfMTyQnQHere's some Porsche abuse...
https://www.youtube.com/watch?v=_dPFkpBbq_E