I have said many times:
"Only restore an engine if it needs restoring."
You'd all be surprised at the amount of work I turn down because I advise my clients never to restore an engine in excellent or better condition - even if it has a few marks, dings or scratches.
My advice: If you want a perfect engine, find an old basket case that's not broken, but well used - in "fair' or "poor" condition - or, even better - one that's been sloppily repainted - and that's the kind of engine we like to bring back to life here at L & L.
In regard to other topics:
Yes, you'll find that circular mark on all pre- & post war Hudsons!
Also: all those high-stack motors will work on postwar engines. The ones Dennis Waldron has are all new old stock [NOS] originals which I believe he purchased from Madison Hardware. They are not after-market motors but were actually manufactured by the Lionel Corporation when the engineering staff realized how woefully underpowered their flagship 773 loco was in 1950. I think the manufacturing of these motors dates to either 1950, or the next year, 1951. As we all know the 773 was dropped from the line after one year and only returned in 1964.
I don't know too much about the later-issue high-stack motors, but I'll assume from both an electrical and mechanical standpoint they will surely increase the pulling power much more than your stock, 1950 or 1964 773 motors..
The high-stack motor is a welcome upgrade to your Hudson loco if you want to operate on any decent sized layout. When I had my layout , my 773 was able to pull 24 freight cars with the high stack motor installed. Without it, less than 10. And grades? Trestles? Fuhhhgeddaboudit!
Best regards to all,
Len Carparelli
L & L MTC
www.lencarparelli.com