carl, i have learned a lot about the starter plate issue recently. i have had minor to major jams with my starter over 36 years with 12 years of on the road driving and no one was able to help me until FTE, guys like ross collord, craig hahn, etc. pointed me in the right direction. look at the two references and see if you can see what applies to you. first off, as you know, your engine may be from a diff vehicle. my truck came with an engine with 8BA heads (car), a cast iron bell housing (usually truck) and what turned out to be starter plate from a car that had a stamped steel bell housing. the cast iron bell is flat and requires a plate with the starter housing parallel to the mounting flange. the stamped steel bell comes down to the crank area then angles back. that bell requires a plate that has an angled flange to bring the starter back parallel to the crank. when you put the angle flange plate on a straight bell, that puts the starter at an angle, causes jams as in my case. the other issue is the size of the crank opening. the 49-52 trucks had a 3.25" radius crank opening and used an aluminum dust shield that was bolted on the two back oil pan threads. the 53 truck and most (?) cars had the 2.12" radius crank opening, no dust shield just a gasket at the crank area (see pics). there may also be a diff in the oil pans for car/truck. what worked in my case was the 53 truck starter plate: flat plate, no angle and smaller crank opening. so far, working perfectly, sounds great, no jams. i crank it with the key off, just to hear it work. with the key on, it starts immediately so i don't get to hear the starter. my pics below show an angle plate and a flat plate. the side view shows the angle on the car plate if you look carefully (sorry my piece of wood blends with the background). good luck and let us know how it works out. i know the feeling when you hear that clunk of the starter jam.
Ford and Mercury Trans Adapters
http://www.flatheadv8.org/bellhousing.pdf