Suggestions for non-Magnum 360 that started running badly?

I was scratching my head on a similar issue a few months ago, and found it was a vacuum leak. I had checked all areas multiple times that I suspected had leaks at and around the engine, but as it turns out the leak was on the brake booster. Mind you I have had booster leaks before, but this time the leak was not bad enough to be detected in a lack of performance or noise at the booster, but was large enough to where it was causing the poor running engine. Leak was at the booster check valve seal. No booster likely on a 62 abody, but thought I would share since it is a resto-rod, good luck.