170 vs. 225

The advantage of a 170 over the 225 is its ability to rev. With a turbo, that is irrevalent. You don't need or want high rpm. Personally I would use what ever engine I had available. That is what I did in 1979. I used the 170 that was in my car, already (didn't have to buy another motor). Used a Corvair turbo, which was used on a 168 cid engine (perfect match). At that time there was very little info available on turbo size matching.