Intermittent 4runner starting problem

I have a 1991 Toyota 4Runner 3 Liter V6 4WD with about 143K miles. About 35K miles ago I got a new engine as part of the head gasket fiasco/recall. Soon after I developed this intermittent problem with starting. The problem started out happening very rarely, then more frequently. I would turn the ignition and the engine would turn over with no ignition. The battery and starter are strong. If I stopped and re-tried the key sometimes it would take a while and sometimes it would then start up. Usually when it started the engine kind of “bucked” as it finally started. I smell gas when this is happening, and when I take a plug off and connect it to the wire and hold it to the engine block to see if there is a spark from the plug to the block there is none. It seems to be an ignition problem and not a fuel problem. The problem is also independent of fuel level.

I have spent a few thousand dollars with various mechanics trying to pinpoint this problem. I have replaced the distributor 3 times, replaced the coil, igniter and replaced the EGR. Mechanics have checked the wire harness and it has continuity. The odd thing about this problem is that it occurs independent of hot or cold, and the problem seems to go away for a while with a new distributor. When the vehicle fails to start most of the time and just keeps turning over, I go to the parts store and trade in the distributor I just bought months before, and the problem solves itself for another couple of months. Whatever the problem is seems to be eating distributors? Any ideas about this problem? All my research has given me no similar problems or answers.