Misfire at cruise, popping/afterfire at 3000RPM

Today I'll be reassembling the front end and welding up the exhaust, hopefully I'll have time to crack into the transmission to swap converters. Once all that's done, I'll be dropping the car back onto the engine (feels weird saying it that way) and I'll be able to continue with troubleshooting. I'm going to start with timing and checking the distributor, and I'll probably readjust the idle mixture screw so it won't be so rich.
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