Okay, I took some measurements on both cylinders. The 72 cylinder was pretty consistent, measuring about 66.5mm to the bottom of all 4 scavenge ports. A little off from the shop manual but the cylinder has not been cleaned up so there may be a little crud on it.
The 74 is another matter. The ports were even left to right but not front to back. Of the four scavenge ports the intake side ports were a little under 64.5mm to the bottom and the exhaust side where around 63.7mm. Not sure whether this was deliberate but, seeing how consistent it is, whoever did the port work must have done this on purpose. Is there a reason the intake side scavenge ports are different than the exhaust side, even though they are right next to each other? I guess that could affect the way the air/fuel mixture swirls in the chamber.
On a side note all the ports on both cylinders were pretty much the same rectangular shape, not like they are shown on the port measurement picture from the shop manual I posted earlier.
Thanks again for all you feedback. BTW, I did look at the Cometic site and they don't list anything for H models. Bummer. I'd have to stack up a lot of base gaskets to move the cylinder up 2mm.
Thanks again for the responses,
Dave