You aren't doing anything wrong with your stabbing procedure, but you need to figure out what is wrong with the cam gear or oil pump shaft. The resistance you're feeling is either because the distributor shaft is not fitting into the oil pump shaft correctly or there is a problem with the cam gears.
To my knowledge there is no difference in cam gears from year to year so the only possible issue I can think of there is the cam is incorrectly spaced so the gears aren't correctly aligned with the hole the distributor drops in to. If it was too far one direction the dist would drop in freely and the gears would not engage correctly, but you would seat into the oil pump. That would probably result in the dist not turning though. If it is shimmed too far the other direction it would wedge the dist gears tightly and possibly prevent the dist from dropping in deep enough to engage the oil pump shaft. Of the two, that sounds like the more likely scenario.
The other possibility is the oil pump shaft has got a burr on it or is somehow deformed and not letting the dist shaft drop in to it. Look down there with a flashlight and see if there is a deformation or maybe even a piece of hard crap fell into the end of the shaft.
You may need to drop the oil pan and pull the pump out to see how it mates up with the end of the dist. If that isn't the issue, use a large flat blade screw driver and see if there is any side to side wiggle in the cam shaft.
Randy Rosetta KDØKWX TLCA #19351 69 FJ40 "Meanie" & 1970 Boss 302 Mustang