I was out your way yesterday.. I took a fide from Boston to Vermont and back and saw signs for winchedon..
I have a 1980 Magnum MK2 also.. it's a 2hp. I also bought a new 15mm Bing carb and they ship those with #82 jets ( I suppose for all the people who install kits... no idea) When Puch sold those Magnums new they supplied two jets.. a #60 for the break-in period and a #58 in a little envelope to install after the break-in. either size will work fine.
Dont forget to clean the round air cleaner element with solvent (it pops out when you open the A/f) and spray a little oil on it afterwards for maximmum air flow..
The stock manifold on that ped is 12mm which is a bit restrictive.. I suggest you get a 14mm manifold (the tall one) to open up the flow of fuel and air a bit because I have a 15mm Bing replacement too and it just seems to run better and smoother with a closer match on the mm size.
The replacements are identical except for the nipple that injects the oil into the engine so if you are going to keep your oil pump setup original you will have to drill it out and tap in the nipple from the old one... I'm planning on doing this at some point but I disconnected my oil pump and I pre-mix because of the pumps age and I didn't trust it...so it's not an issue now.. I've since gotten a brand new replacement pump so I'm planning to re-install it at some point in the future (and use a little oil in the gas for good measure) but I'm having way too much fun on the thing to stop riding it long enough lol
Good luck... and lets rally!