Thanks for the lead on that, I did some checking and got this:
The front bushing for the 41-50 is 1" long, the 51-54 is 1 3/16" long.
Easy to check- I slid a bent wire in by the shaft and caught the back edge of the bushing, then marked the depth and measured it - got the 1 3/16" bushing!
This means my '50 code torque tube has the '51+ bushing, so it's a late '50 year change to watch out for.
For what it's worth, the "Ask Jim" responder advised to use the incorrect '50 replacement based on the code only , even though there was no dowel pins. I plan on advising them of this when I order the '51 bushing
