1959 G3 piston and big-end

[33d6]

Hi Alan,
To be blunt, you don't order a replacement piston.You take the cylinder and piston along to a reputable engine reconditioner and ask them to inspect and measure the bore and piston and then go from there. They will advise on the condition of both and after measuring the bore will tell you what, if any oversize will be required. it is a rather pointless exercise putting a new piston in a worn bore.
Much the same applies to estimating bigend wear. Most engine reconditioners are only too happy to explain what they look for and why. Of course I mean the actual firm who does the work, not your local joe who just acts as middleman and sends the work out.
I don't mean to sound rude but if you have to ask this type of question then you really need to seek advice from people who do the work and can see and handle the parts in question. This forum is not really appropriate.
Best of luck, BOB