Fortunately the issues you are having aren't design related, so once resolved you should be fine.
Based on the sounds of things mainanance wasn't somethimg the PO sepent much time on, and whern he did, he didn't care about doing it right. Since you aren't aware of what the service history is, I would start with a good tune-up, plugs and wires, valve adjustment, cap and rotor,timing chain, carb rebuild/fix the HAC or replace with an aftermarket carb. Once done, you should be able to set the timing correctly w/o advanced and have it run smoothly.
