Do you mean a Hotair Turbo Regal Year with a Intercooled Turbo regal motor?
If it's a IC 86/87 motor, i would say any turbo can fit, depending on how you want it to spool up, what injectors you have, plan on having, Chip, Downpipe, wastegate, skys the limit. You have many many vendors that support the IC motor so many parts to choose from, turbos, cams, whatever. So to answer your question any size would fit. It all depends on what your goals are. Cruzer or Drag demon from hell, trick is a TR is both
If it's a hotair that's been intercooled (stock turbo location) i say few choices, ex TA33.
Again supporting mods would be/ have to IMO are fuel pump & hotwire kit, TT chip, Adj Fuel pressure regulator, bigger injectors(ex 50lb) Alky.
You want your turbo to max out before your fuel system does IMO