Distributor Install question

I am changing over my prform HEI ignition system to a MSD set up. For some reason I can not get the distributor to seat properly. I have read several posts and tried everything including bumping the engine, and moving the oil pump shaft. I can slide my old distributor right in.. .no problems. I can't even get the distributor to make contact with the cam. So as you can tell...it barely goes in at all. Its an 86 motor that I have converted to carb. MSD distributor part number 3479. Any ideas?

Yes, everything matches

The speed shop that installed the gear said that they measured from where the flange of the distributor seats against the block down to decide gear placement. I just noticed that the distance from the bottom of the gear to the end of the shaft where it meets the oil pump shaft is about 1/8'' longer on the new shaft.. I wonder if the angle of the distributor is not allowing the distributor shaft to go into the hole where the oil pump shaft is..?