Hell yeah, I hope I'm still messing with mopeds at 50!!!! Welcome to this forum
There are a million different combinations of cylinder kits, pipes, carbs, ignition, etc that you can put together and achieve what you are looking for. It's actually kind of insane how many parts are available for Puch e50 engines. In my experience, 50mph is about the cut off before you need to start pushing the limits of reliability, so what you want is feasible.
With mopeds, the simpler the more reliable. So i would say go with a piston port kit. No reeds to fail, and less potential for air leaks. 45mm Treat 70 kit is a bullet proof single ring kit and unported you can hit 50. Treatland also sells machined heads to match this kit, get the o ring one and you'll never have a leak.
Going to need a better crank too, Treatland has nice unstuffed ones.
The stock Bing carb that comes on Puchs arent the worst, but 50 might be a stretch unless you bore it out. If you decide to buy a bigger carb, dont get another bing though. SHA carbs are very simple and depsite what some Puch lovers say, they do work great on an e50. #7 slide is the key though. 15 or 16mm will do, they make an intake for them that bolts onto the Kstar cylinder. Any bigger is kind of overkill for what you want.
Pipe, maybe something like the MLM peoples pipe. Homoet 6p is a great pipe too for small carb high revving set ups.
Stock bosch points are reliable if maintained. Set your gap, you can rotate the stator to advance the timing if you kit it.
As for gearing, you should be able to hit 50 on a basic set up like I described with 17x45 gearing. That is a nice blend of low end and top end on a kitted e50.
