Going by memory here , but I believe the years where they were building 74's and 80's , one had 7.4:1 and the other was 8 or 8.5:1 , do you remember ??The typical Weisco "high compression" piston kit for a Shovelhead is only 9:1, and is quite manageable (e.g. no starting issues or other ill behavior). I had a set in my 82 FLT that I rode to work daily back then, and it was stone axe reliable. I wouldn't worry about that one a bit.