Are we talking with engine mods or not??? i.e. forged pistons, cams etc
No idea what the maximum power one will take 'standard' before reliability becomes a concern.
The FRP has c153 bhp so c30 bhp more than the standard Puma (123 bhp) but it'll cost a fair bit to get the parts to put a standard one up to the same spec.
Mine has 173 bhp when running a 50 bhp shot of nitrous and I'm going to be upping that soon to a 75 shot so 198 bhp in total but I've seen much higher. Plus it's only there when wanted and not all the time which may be a plus or minus depending what you want.
You could modify the engine up to a decent output but it all depends on your budget.