What kind of mods, and why?
I'm running a Rev 1A motherboard, if that means anything.
That's the best board revision. It won't need ANY timing fixes.
By an ACA1232@33MHz with 128MB ram from Amigakit. You won't regret it.

Unless you need an FPU? ACA1232 can't use an FPU. I'm mentioning this because you seem to have specific software in mind I think? FPU's are pretty useless though as far as I'm concerned.