Very puzzling-STOCK DISTRIBUTOR WON'T FIT

I got a 1987 Chevrolet K5 Blazer with a remanufactured engine. Less than 500 miles after the engine was installed, I started having problems with the distributor. I remember when I picked up my truck they told me the reluctor had cracks all around it and that I should either replace the reluctor or the whole distributor. So I bought the whole distributor and I asked a friend of mine to install it, it refused to fit. That seemed odd. I returned the new distributor and brought my old distributor to the parts store to find out which part would fit. I found out that the parts inside the distributor were from a '94. I replaced the parts inside droped it in and the problem was gone. It's been 1500 miles since then and the problem is back, same diagnostic code too. CODE 43. Sometimes it will fire right up, sometimes it struggles then starts, other times no spark. I'm still trying to figure out why a '87 distributor won't fit a '94 engine. I never compared the '87 and '94 distributor side by side. Anyone familiar with HALL EFFECT DISTRIBUTORS?

 

I forget now, have not had them sitting beside each other. But I think one is longer in the shaft. So the intake manifold might be off a newer the 87.

 

The intake is the original. The remanufactured engine is just a long block. Everything else was reused from the old engine.

 

The only other thing I can say is take a pic of it. and I bet I try to show the 1975-1987 Hei dist . The housing is basicly the same except for a opening for a extra set of wires. Then the top part of the base of the dist is different. I know there something that not set up right or wears out cause that to happen but I forget for sure what it is now I rearly work on the 88 and up dist.