Scott, This will not be a one mount fits all scenario. It matters what engine and how Lionel did it. PW Steam is different from Modern Steam with AC motors. Shell size, how the drive works, etc... I seriously doubt the average hobbyist can take this project on. You may want to reach out to Frank to see what his demand is. Then again he may not share.
Your motor selection is fine for upgrades and repairs. My recommendation is having double shaft motors of your style, and 5 pole vice the 3 pole variation. Early Williams and others used 3 pole and also different ratio.
Many of your steam have Flywheel in back, yet Williams MTH have them in front on most. Having double shaft allows the installer to choose where flywheel goes. G
