Removed distributor on my '91 Firebird 5.0 TBI to replace pick up coil. Me & 2 buddies have spent over 10 hours trying to get dist back in. Won't drop that last 1/4" onto oil pump shaft. Never had so much trouble installing a dist before. Any hints?

 

Assume you know to index the pump drive shaft, so that it's slot lines up with the tang on the dist?

If that's not it, I had a different issue once. Is the car on a slope? I had to change the dist with the car in the street parked on a downhill slope, rather than on the flat in the garage. It was enough to tilt the pump shaft forward just a little, and make engagement nearly impossible. That took me a couple of hours before I twigged to it.