The 2.3 is a good motor. I have run them in my rail buggies for over twenty years. The bottom end is bullet proof!
My current set up in my street /off road rail is pushing over 225 hp with a single carb induction.
It is realistic to get over 300 hp with a stock IHI turbo on a modified motor . The last turbo 2.3 i built was mild and pushed 20 lbs boost with an un-modified{except for locked by-pass valve } IHI turbo.You really can't hurt these with 20 lbs boost. A stock turbo-coupe has 190 hp, add 20 to that with just a cold air induction. Any hp. over 350, turbo,nitrous or natural aspirated is going to require major head work or an aftermarket head. Both Esslinger and Racer walsh are good sources for these motors.
I also have a couple of turbos for these if you are interested, you can pm me.