The absolute best upgrade I did was a Petronix electronic ignition conversion 15 years ago. I will never go back to points if there is an electronic conversion option available. And, since I'm an enabler, I've helped a handful of friends convert points to electronic ignition. I was worried about reliability so I shrink wrapped the original points and all and tucked them away under the bow, but I've never needed them.
Other than yard tools, I have one engine with a carburetor; a Holley 4160: 600 CFM double pumper. I don't trust anyone working on it but me.
A few years back I looked into an EFI swap but it is a marine application and not only expensive, complicated to get sensors installed with a wet exhaust. Besides, the carb is pretty fool proof since I set it up correctly.