So far it hasn't needed much - points and plugs and such. Mack carries parts for many of their old road tractors, but I kinda doubt pickups back to '41.
So far a proper tailgate has been elusive, although I haven't tried very hard to find one. As far as "They don't make 'em like 'em used to" - the cast brackets that hold up the headlamp - 1/4" thick iron casting. Apparently they weren't too worried about weight back then.
I too love Power Wagons. A high school teacher had a WW II Dodge 6X6 in very good condition, unrestored. A bunch of us used to help him cut firewood 'cause he was a cool guy, it was something to do and we got to ride the 6X6. (Nintendo & text messaging hadn't been invented back then) I think top speed was 40 or 45? In recent years he got into a bit of a public relations jam because he at fifty something married a former student of 20 something. (I told you he was a cool guy

)
The truck show at West Springfield, MA is 2 hours south of Bennington. One can either run the slab (91) or take the back roads to get there via 7 to 8 to 112 to 20 etc. The back roads route is scenic, although not nearly as mountainous as the beautiful Green Mountains of VT. Both ways are right around 2 hours.
Even more trivia - we had another one previous owner locally based Mack pickup in very good shape. It got sold to Eiler's Bros in Readsboro, VT. While I miss the 2nd Mack and didn't want to sell it, it did go to a very good home. I don't know if the Bros are still alive and well. Hopefully someone is looking after their awesome collection.