I got into the cart world as an off shoot of the NV world. My hunting buddy is about 15 years older than I am and hates walking a lot more than I do. He bought a 2006 or 2007 Bad Boy Buggy ("BBB") Classic about 3-4 years ago. The frame, steering wheel, wheels, plastics and roof are still original. One of the motors is original.
Lots of new tech in the golf cart world. Yamaha came out with an AC electric cart that still uses lead batteries with an IRS a year ago. The aftermarket lift kits are just starting to show up. Yamaha also introduced a gas cart with EFI that has a "quiet tech" option available. Not as quiet as electric carts, but pretty damn quiet. Same issue with the lift kits on it- I've been in the market for one for 2 years waiting on lift kits for the AC or Quiet Tech carts. From my research, the new Yamahas are just the best two wheel drive option out there.
From using the BBB to hunt out of the last couple of years, I've noticed that the ATV tires make more noise on gravel than the rest of the cart does. The Yamaha Quiet Tech's I've test driven on pavement are quieter than the BBB on gravel.
For anyone even contemplating a used BBB, you need to own a welder and lots of tools. BBB started out buying fleet carts from EZ GO and then EZ GO bought the BBB company. Wiring diagrams are extremely hard to come by, and most I've actually been able to get are hand drawn. There are two types of the older models- one version has one motor that powers all four wheels and the other version has one motor for each axle. The main computers are called controllers and they are freaking expensive. On any cart, lifting it and adding larger tires almost requires an upgraded controller, solenoid(s) and battery wire gauges. Oh, and they're freaking heavy. The BBB we've been using uses 8 six volt batteries that are a little bit larger than a half ton's auto battery. About 700 pounds just in batteries that require careful regular maintenance. The BBB, at least the one we've been using, is the torquiest thing I've ever driven, and it will literally drive up a tree. That being said, its replacement WILL be 2x4.
Club Cars and EZ-GOs have a lot more aftermarket stuff available than the Yamahas, including a very aftermarket posi-trac system and lots of very capable lift kits.
If you want to go completely custom, there are a lot of guys using recalled Nissan Leaf Lithium battery packs to retrofit (or even frame off) existing carts. Lots of information available at Buggies Gone Wild . com.
For the best custom build I've seen:
Yamaha Lithium and
More Yamaha Lithium