I don't think you understand, Chevy Nova's are probably one of the easiest cars to work on. Changing an alternator would be like nothing, same with the battery. Also I don't care about the sound system or anything, it's not a entrepreneur -mobile. You're comparing a 1999 to a 1973. So much more simplistic, this 73 is. Not all this electronics stuff that you don't even know what the hell it does, all you know is that there's a part number on it so you replace the whole damn thing, instead of actually figuring out what's wrong with it. Replacing a tachometer back then would be crazy, guys would just take it apart and take the time to figure out what could be the problem, not take it to the car dealer just for a damn tach. Welcome to the 21st century of cars and their owners. Times have surely changed. 
cars didn't really start getting absurdly complex until you get into luxury cars and cars past 2000ish when they started putting all sorts of bits into it. the only real difference between my car and the gremlin my dad drove as a surfer is that i have an air conditioner and power steering fluid. there's just less room to work with, because cars aren't meandering land arks anymore.
i swapped out the sound system because it would spontaneously stop working when listening to the radio, so i'd be driving in total silence for hours on end; it's mind bogglingly boring. i would have swapped out the alternator myself, but it's buried behind the engine and under the air conditioner so yeah forget that, i'm not going to spend 5 hours removing half my car to pull out a 2 pound hunk of semiconductors, replace the engine, try to wrangle the belt on, then replace the air conditioner.
when i had a 1992 chevy pickup truck, i replaced the old rusting radiator by hand. never again, holy stuff. trying to get the rusted bolts out from their holes, then trying to wrestle it out from below the car because it rests under a lip in the hood, then cutting my hands open because there's a 2 inch wide rusted hole in the bottom of the radiator. then, after removing it and immediately throwing it into the garbage, i had to wedge the new 120$ radiator in, re-drill in new holes because it wouldn't fit into the mounts because the old mounts were warped, then i had to fill it, wait an hour, then fill up the reserve tank. ugh.
what i'm saying is that to buy an old car, you're going to have to put far more money into it than to get a used 90s or 00s car. i wanted a gremlin x as a first car, but a decent one cost twice as my current car which is 20 years newer, and with a car as old as the gremlin, you
will get tons of grounding problems, overheating, and so on. you also get parts availability issues, where you have to special order parts or get them online. i had trouble finding parts for my pickup, and it was a best selling truck in the 90s.
also, reliability. in the 70s and 80s my dad was lucky to get 100,000 miles out of the cars before everything started to go wrong, the roof started leaking, engines ram their cylinder heads through, and all sorts of lovely little things. the pickup i had was in terribad shape (rust loving everywhere oh god) but it was still vaguely working at 250000 miles, if you ignore the giant hole in the radiator and the suspension fused solid to the body.
