Thanks Wrench!
I crawled under there today for a bit and came to the same conclusion after a closer look. There isn't much of any slop due to bolts or the holes in the starter/bellhousing.
My dad had another suggestion, that maybe the new switch I installed was latching and taking longer to release power to the solenoid. Per his suggestion, I hooked a voltmeter up to the 'S' terminal and watched as I cranked. It doesn't seem to be the culprit as voltage drops off very soon after the button is released and there is no voltage while the engine twirls the starter gear.
I still need to bench test the unit; hopefully can get to that in the coming days.
One thing to note, I'm not sure if it could affect things: the engine hadn't been started in over a year so after I got fresh oil put in it, I spun it with the starter for a few pulses without any plugs in it. Without compression, the tach was showing nearly 1000RPM. I did maybe 5 pulses of 3 seconds each.
Nothing seemed to be stressed during the process, I figured I was doing it a favor. Does anyone think these antics may have stressed the spring/bendix assembly? Hopefully I can inspect that better once the starter is on the bench.
All said, I'm still hoping it's not an alignment issue...I just don't see how to shim this older style mount. Alvin had mentioned using shims on this style before but I could not for the life of me track any down last night. Plenty of shims for straight/offset block mount starters but none for the bellhousing mount style.
