What happened to make you think you needed to replace the piston? You're really going to have to get answers to the basic questions or replace parts until it's fixed. You said a few things that are contradicting; you blew your top end but you were just planning to over bore for performance reasons, is the biggest red flag. You can often re-ring with a hone to bring performance back up near peak levels if you do it when you feel power loss but once it's to a point that the compression is so low it's hard to start, it need bored and an oversize piston is needed. Needing a new piston can be found with a compression tester or obvious damage to the cylinder, piston or rings. If your cylinder was good and you didn't test the compression, how did you know you needed a piston? If you had someone with the tools to accurately a cylinder, you probably have access to a compression tester. A lead tester is more of a specially tool, I understand locating on can be a little harder. Most of what it takes to build one can be found laying around, or at least suitable substitutes. A low pressure gauge is the exception and probably most of the cost (I didn't have to buy anything when I made one, so I'm not 100% sure) but if you can get together everything except the gauge, I'll send you a good low pressure gauge for free. I bought several Ashcroft 0-15psi gauges a year or so ago at a good deal, just for this purpose. Look at one of the threads on building a leak tester and see what parts you can come up with. I might be able to help with more of it if you can't get ahold of all the parts you need.