Welcome to CHR!

I’m making an assumption this is a stock SBC – if so, this steps below take care of 75% of all “run-like-crap” issues on an otherwise healthy engine. As others have already suggested, it’s time for a basic tune up.
• New distributor cap
• New rotor
• New sparkplug wires
• New sparkplugs
• OPTIONAL – new HEI module for “peace of mind” as they rarely go bad. Adds $30-$40.

Check for disconnected or broken vacuum hoses – and reconnect/replace as necessary.

Also assuming you have not moved the distributor, you should be able to install the above components and in all likelihood, resolve your issue(s). I know this may sound basic, but take your time with the replacement of the plug wires and go one at a time.

Firing order is: 1-8-4-3-6-5-7-2. If you get that out of sequence it will run really bad.

Once the above is completed, put your timing light on #1 (with the vacuum advance disconnected and plugged) and set base timing at 8 degrees.

Good luck and let us know how this goes!
Glenn