[Ronnieroadster]

Its important to check the outer edges of the piston to the dome of the head. The Ross piston top radius is usually not the same as the dome of the heads. Not sure how much of the dome you have checked so I will explain how I do it just in case it helps you.
I always use clay material placed on top of each piston. Here's how I do it I place the clay in four locations one dead center of the dome then along this center line I put clay on each side of the dome as far out towards the outer edge of the dome as possible. The last area I clay is at the bottom center of the piston once again as close to the outer edge of the piston dome as possible. Its important to do all eight pistons to the domes of the heads. Now you can rotating the engine enough so all eight pistons are at TDC during rotating the clay has now been compressed to the clearance dimensions. Once the heads are removed simply use a razor blade to slice the now compressed clay along its center line remove one side of the clay exposing the edge of the clearance. Now use a Vernier caliper placed on the edge to measure the true clearance at all for locations of the piston tops. Also I use the clay for valve clearances measurement as well
If your block was not decked off the crank center line you will find from side to side different readings. If the head gaskets your using are copper composition type you can reuse the gaskets after your checking is complete I always check clearances using the head that will end up on the engine. Just be sure to use the same gasket on the same side you used for the clearance checking to keep things equal when assembling the engine. Using the aluminum rods on the street can be done without any trouble {I have thousands of miles on mine} however you will find the engine will rev up nicely but the down side is this may effect your fuel economy.
Ronnieroadster