Depends if you want to do it yourself or not on cost
Parts wise you'll need good cam (Piper 285 kit is best)
T28 turbo of some description, you'll need to run fairly high boost (22-24psi)
Poss drop compression very slightly (only if needed)
Very light flywheel
Well jetted carb (not a grp A)
Ideally a 2 1/2" exhaust and downpipe
Front mount intercooler
Good fuel system, phase 1 pump or maybe surge tank set up
With it all set up right that will get you in the right area for 230bhp but may need a few slight tweeks here and there