I was just reading an ASE 8 training manual and it stated that in 1999 the compression ratio was changed to 19.5:1. I am assuming this was done with the pistons or the heads since the bore and stroke are the same as the other 6.5s. Does anyone know which it was and would 19.5 be as good/better CR to shoot for with the GM heads or pistons (which ever it was)? Which would be better the 19.5:1 or 18:1? Seems the GM parts would be less expensive than the aftermarket 18:1 pistons!? Are these GM parts hard to come by?