Both good questions, I'll toss in "how much do you want to spend?".
a very very popular and easy upgrade, if not done already, is to upgrade the ignition to HEI and alternator to a newer, stronger, less maintenance '1-wire' alternator setup. Lots of threads on here for each, and each can be done for only $100-200 each depending upon how fancy and name-brand you get.
...and it should go with out saying but, first and foremost, make that car safe, then reliable. So, check brakes, brake lines and fuel delivery for no leaks or rust issues. (a good fuel filter is a good start too)
Then, on to the upgrades I mentioned above.
These cars were made before President Jimmy Carter proposed adding alcohol to fuel to keep us from being held hostage to the Gulf States (middle East not Texas and Louisiana). Because they were all made of rubber and not a petrochemical plastic they are susceptible to attack by alcohol and will leak like a sieve. It has to have a blue plastic Teflon sleeve on the inside to stop the attack of the alcohol.
This goes for Chinese stainless steel braided RUBBER hose as well:
Gasohol also attacks the metal that carbs are cast out of unless they are anodized to protect them. And you though they were colored to make them pretty!
This also explains why your lawn mower only lasts one season of mowing and won't start the next spring:
It attacks all carbs except those that are anodized. It is why you should also replace your zinc clad fuel lines with stainless steel because the alcohol will eat the zinc off of the galvanized fuel line leaving only raw mild steel that will rust (same for the fuel tank itself).