What should I do to my old inline 6..?

[LandonL]

Alright, it's 43 years old, temperamental as hell, never been taken apart, and I don't know enough about engines to know what to do. Problem is, it's always wanting to die, (Yeah, the timing on it's fine) it's always wanting to choke down, unless your just driving down the road. When you come to a stop sign, it sometimes won't choke down, or it'll try but it's always something.. I'm guessing since it's 43 years old, never been torn apart to be rebuilt could be part of the problem. A friend told me 43 years of carbon build-up on the pistons probably isn't good. Say I took a leap of faith, pulled the engine myself, what would I ABSOLUTELY need to replace, and what would I need to clean for it to run smooth all the time. Also, after cleaning the engine I'd install electronic iginition & new exhaust. So anyone's opinion would be great! Thanks. Is it something I could do myself?

EDIT: The carb has been rebuilt within the last 6 months