Actually I think the cutouts are misleading. The battery in my caliper seems to have died, but the intake valve measures about 1.75 across so I'm assuming they are stock 1.78 valves, unfortunately.
I'm going to check the compression hight. Just from eyeballing the carbon ring in the cylinder looks to be around 1/3 of an inch, possibly more. If these are the pistons I think they are, compression distance will be 1.720.