My upgrades to my '66 Beetle have been (so far) limited to 3-point seat belts at all 4 positions, a dual-circuit master cylinder, gas shocks, an original EMPI Camber Compensator (it's a swingaxle thing), radial tires, Pertronix ignition and I've converted it to 12-volts. It drive exactly like it did when it had a single master cylinder and point trigger ignition, but it handles appreciably better with the shocks and Camber Compensator. I mostly did that because I plan on later upgrading the engine to something more than double the stock horsepower, so naturally it will have more compression and be harder for the starter to turn it over. Of course further brake/tire upgrades will come along at that time too, along with something to replace that rickety stock shifter. I will not, however, drill any holes or cut anything from my clean original paint car and I've kept everything I've taken off of it so it can be returned back to bone stock if I (or a potential future owner) would so choose.
Is that heresy? To some I'm sure it is, but as a hot rodder at heart I'm constantly torn between what I want to modify and keeping it bone stock. When I finally decided to make bolt on mods I felt really good about coming to the decision, so I knew it was the right one, at least for me.
Kyle, the much missed Richard Lentinello when he was Exec with Hemmings wrote an excellent article in Classic Car, their sister publication, about updating your older car. I think it was Issue#150 but I'm not sure. I have made a practice of adding disc brakes at least in the front. I had a Thunderbird that rode like a truck; I lengthened the springs and it was much more comfortable. Electronic ignitions. Air Conditioning if I drive it a lot, and so on. The point here is to add those things that make it safer and more comfortable without destroying its identity. Because I drive my cars. They don't just sit. Stay well.
If you drive farther than the edge of town, overdrive transmissions are great. I put a 5 speed in my 50 year old Camaro, if it didn’t have the shift pattern on the ball you’d never know to look at it. 75 mph at just over 2000 RPM.