trouble reinstalling distributor

After swapping intake mainfolds. I noted the rotor orientation and I can feel the worm gears engaging as I drop the distributor in. It's bottoming on something. It only goes as far as the bottom of the o-ring gastket and stops. Gentle tapping and wiggling doesn't seem to help. Any ideas?

Thanks.
 
It sounds like it's stopping on the oil pump driveshaft. You can do one of two things. Use a socket and turn the shaft a little and try putting the distributor back in. Or you can put the distributor in until it stops, then turn the motor over until it drops in. That's the way I usually do it.
 
If you use the socket method, use a 1/4" drive one, and duct-tape it to the extension. If using the starter method ( this doesn't always work for me and is hard on the oilpump drive) just bump the starter with a screw driver across the solenoid terminals while applying pressure on the distributor.