base timing keeps advancing by itself...
Thanks for the tips. After confirming TDC, I went back in to take a look at the carb. Did a full throttle pull, killed engine and pulled plug, it showed almost completely clean. Ordered needles (Edelbrock avs) to go richer. Will see how that effects things.
I'll admit, my post is probably overly cautious/alarming. The thing is, it's too easy to miss something small and have things go horribly wrong as a result. It's unlikely, but the possibility does exist. If a carb is dumping fuel, or isn't flowing enough, then damage can definitely happen. Fuel wash of the rings can happen quick, and undetected knock can crack a piston or burn things if it persists long enough.
Sounds like you're on the right track though, and with your new observations and checks, you're likely to find the issue quickly.
If the car did run better/different in the past though, needles and jets may help but may not be the root cause. Edelbrock carbs are easy to pull the tops off and you could pull the booster assemblies. If I remember right, there's a lot of small holes on the elumsifiers which can clog up when left in storage for a winter. Might be worth checking those out, as well as ensuring the inside of the carb is in good shape.
Be careful of the accel pump check ball and weight though. Easy to lose them into the manifold if you're not familiar with them. I've also had the accel check ball stick in the seat and cause issues while accelerating. At the same time, I had lots of varnish in the idle transition slots which caused the idle mix to be non functional, and caused a lean surge at cruise. I'm not saying these are or could be your issues, but the same thing could affect various circuits in the carb so it wouldn't be bad to do a thorough check and clean.
I'd changing needles, jets, and springs help it could be that they're the fix, or they may just lead you to the real problem. Personally, I think it's a great path to start down. I'd follow the others suggestions since they're far better versed in tuning than I'll ever be (I gave up and went efi, lol).