A new piston is going to cost you $50, minimum, bringing your cost for this kit up to $90, and that's even before you figure in the cost of boring the cylinder. So much for your 'deal.'
A puch metra 80 is old tech dude. It's essentially the same design as a stock cylinder, just with different port sizes and timing. I could go on and on about this, but I've already done so in <this thread:https://www.mopedarmy.com/forums/discuss/read.php?f=7&i=156988&t=146892>. Also, statements like "no need for a reed valve haha" make you sound ignorant. It's great that you're excited about your kit, we all were, but try not to sound like a douche about it.
Seriously though, good luck with your kit. That's a big-boy kit, and you'll need to learn a lot to tune it correctly.