piston question

this is my first post, excuse me if i mess up terribly.

Anyways, I have a skyhawk engine from jake's. it has 40mm intake and exhaust

spacing. It also has a 40mm stroke making it a 68 point whatever cc. it came

with a Z-L rod and what appears to be a skyhawk piston (10mm wrist pin. 7mm

from skirt to pin. 12mm long skirt with about 24mm between skirt cutout. I would

like to get a new piston. Will the number 5 piston work? who sells original grubee

skyhawk pistons? the only place i found was custommotoredbicycles.com

any help or info would be very appreciated, thank you

so the number 5 won't work? the only number 2 I have seen is for 50cc. what is meant by oversize

thank you for your response

thank you. so it is more a measurement of machining tolerances, correct. I just noticed that certain vendors: bike berry, gas bike, custommotoredbicyles, referred to pistons by a number. I've seen number 2,4 and 5. thank you again this has been most informative