[Engineer Ed]

OK, here are the basics.

I have a 351W that came out of a 1997 F250.
This is a "Factory Roller" engine.
Custom grind Comp Cam with "non-steel" gear.

I was instructed by Backdraft Racing to get an MSD Pro-Billet distributor P/N 8578

I went to install the distributor and it will not drop down far enough into the hole.
The length of the distributor shaft is 5" long and the depth of the block for the distributor is only 4"
The "gear" on the distributor is about 1" from the bottom of the shaft, but when you look into the block, it appears that the gear should be relatively close to the bottom of the shaft to mate with the cam gear

I dont know what to think....
Would the later model 351W engines be any different than the pre-1995 351W?
Could MSD have sent the wrong part?
There is a label on the part that lists it as a 8578.
This is frustrating...

Need advice.
Thanks,
Ed