I agree that the best thing would be to pull the head and have it checked along with the piston. However, time is of the essence and around here machine work takes two+ weeks to turn around for non commercial customers. If the swap is a matter of changing engine harnesses, and swapping all of the engine components and sensors, that may be my better bet.
If I have to change out the dash wiring harness as well, plus make all kindsa mods to get the thing to work, !@#$ that, and I'll be without a car for a while longer.
Ford tended not to make too many modifications between individual years unless they made radical, obvoius changes to the entire car design. Since 88 and 91 ponies are in the same model year class, I thought it may work with minimal effort.
Being the engineer type that I tend to be, I was doping out the research first, then making an educated decision on which avenue to take. I hate getting in the middle of a project and wishing I went the other way.
Thanks for the input, that's one for engine teardown
