Just do your research. The nylon gears are fine, although I've not heard anything bad about the metal gears. Ma Moper thought nylon was fine and they held up in millions of slants for bajillions of combined miles.
That said, be careful what you call an "upgrade". This is where your research comes in. When I did the compression test on mine right after I got it in January of 2019, all was well, so I did a major tuneup including a reman distributor. I disassembled it and gave it the once over and surprisingly, it was a really nice job. @hallifaxhops also fixed me up one with a performance curve that I may go ahead and swap in the little 170. I may not. It runs dang good as is.
Biggest thing to remember from all this hoorah is be careful what you call an upgrade. It may well not be.
