If you want to keep it simple and dont have the tools to measure clearances or have alot of experience building these engines, id suggest starting simple, which I think is what you want after reading your post.
Billet rod isn't needed if you are just going to play around in parking lots and not turn alot of rpm, but if you do choose one, id go with a stock length rod.
Better carb, such as a Mikuni 22mm or other slide carb around 22-24mm size, and jets to tune it, dont forget the carb manifold and air filter for it
Billet flywheel, use a stock timing key, that will be plenty for a torque engine
Black mamba JR cam and 26lb springs from smallenginecams.com, keep it simple and keeps the power down low where you want it
Top plate, fuel pump and throttle linkage kit, to make it more simple and get rid of the stock gas tank, which usually causes people problems anyways, and make another fuel tank for yourself.
That should give you plenty of low end power to play around with and possibly get yourself into some trouble, yet still be reliable and not give you a bunch of problems. Unhook the governor and take the low oil sensor and governor parts out, seal up the holes, put it back together and keep the rpm under 6500rpm, it will last for years as long as you keep clean oil in it. You can find a small tach on eBay that shows your rpm so you can keep track of it. Go have some fun. Also, be sure to use a good torque wrench, I like to use red loctite on the bolts, 17-18ft lb or 220-225 in/lb is what you want to torque headbolts and sidecover bolts to, the flywheel needs to be around 70 ft/lb, I prefer 80 myself. Be sure to tighten the headbolts and sidecover bolts in a cross pattern like you would lug nuts on your car, dont just do one after another...once all are tight start back at the first one you did and check them all again. Be careful not to overtighten the carb nuts, valve cover bolts or the bolts holding on the recoil shroud, only tighten those a little past hand tight, or around 75-80 in/lbs of torque. Good luck
