^^^ Thanks for that. Just measured the MSD with the thrust collar/shaft pushed all the way against the body. I get between 3.069~3.066. While it look as if my gear is possibly a good .019 too low on the shaft, I don't think that's my present issue as the resistance starts immediately as soon as the gear on the dizzy engages the cam gear.
That's pretty far off. If you look into the distributor hole in the intake, you should see a shelf on the block that the distributor gear rides on. The gear gets pulled downward as it rotates and sits on this shelf as it spins. If it's too low, the gear would be pushed down on the block shelf and would bind when the hold down bolt/nut is tightened. If it's too high, the gear won't reach the shelf and the bearing in the distributor would wear out quickly as it would be taking all the downward force.
There is only a bit of leeway in gear placement on the shaft. The less endplay the distributor has, the more accurate it has to be. The stock distributor has quite a bit of endplay. I don't recall how much the MSD unit has.
A Crane distributor I have had almost no endplay so the gear placement had to be dead on. It was way off from Crane and would not have worked as is.
If you have turned the engine over with the MSD distributor bolted down, you might look at the bottom of the gear to see if you see any sign of wear. Also if you can measure the distributor shaft endplay on the bench, you can compare the number with the distributor in the engine. There should still be shaft endplay up and down but the number should be smaller than on the bench. If you measure this, you have to make sure you measure the actual shaft endplay and not the slop in the advance mechanism.
I guess there's always a chance MSD might have made an error and stuck a gear from a different engine on there. If you can't get a gear from MSD, Crane makes a steel gear for the bigger MSD shaft that works with flat tappet and roller cams.
http://www.cranecams.com/userfiles/288-290.pdf I would think if the gear is the problem, MSD should make it right.