Need some advice with my piston swap.

Using telescoping gauges is a real PITA, but it can be done. Personally, I'd spend a few bucks and have the machine shop measure the bores and compare to the specs for the pistons you want to run. You'll know real quick where you stand.

If you plan to do this more than occasionally, consider investing in a dial bore gauge. This one should be just fine for automotive inspection... http://www.shars.com/products/view/2196/26quot_Dial_Bore_Gauge