I removed the electric start from the pony motor, but unable to seat it fully when re installing it.  Any hints?

Where the nose of the motor goes into the hosing? Think you just clean any rust and dirt off apply a little grease note where the hole in the starter is remove the pointed bolt and slide it in until the holes line up then tighten the bolt enough to hold it in place and then the lock nut up ..hope that helps..

If it is starter into the round bracket, get it shinny. Wire wheel or emery paper to get the rust off. And some lube as cheshire cat says. I have put anti seize on it, rather than oil.

Thanks for the replies, I removed the entire starter by first removing the single retaining bolt.  I haven’t been able to get back to it but I have a theory, before removing the pointy bolt I removed the two bolts holding a backing plate that sits between the pony gear and starter, then reinstalled the bolts when I realized that’s not how you remove the starter, I think I introduced an alignment problem.  I will post an update in a few days.

Use some caution when trying to put it back in place. As everyone else said, shine things up very good, and use something like Never-Sieze in case you need to pull it out in the future.
I had a bugger of a time removing one last week, short of using heat. Pinch bars, loose juice and a 4# sledge-O-Matic and patience. No swear words. Good luck. JM

Thanks again everyone for replies and encouragement.  I was able to get out there again today, got everything aligned and the starter installed, the pony fired and diesel running, it’s a 53, still going strong (unlike me who is also ‘53 but wearing out fast .