I had engine overhauled for worn rings 6,000 miles ago but had been burning oil real bad before that & smoking due to that. Catalytic could be likely, right? from smoking long-term that could've clogged catalytic couldn't it? I've on very few occasions smelled rotten egg sulpur type smell I'm told is common from bad/clogged catalytic converter.

Also if it was distributor how hard is that to check? it's been a long time since I had the distributor changed.