I've had a bunch of American bikes, the oldest was a 1915, the newest a 1993. Not long before we moved back to TN I was GIVEN a 57 FL, in a VL or Knuckle frame (based on how bashed the seat tube was to clear the rear head), with a 21" spool in a real Knuckle springer. A week before we moved, I gave it back to my friend Nitro and told him good luck. Even making good money I wasn't about to drop $24-28K into ressurecting it, and it was complete, with great compression. A few inquiries with the title office and I found how just how hard it is for a former patch holder to get papers on a pre-70 engine, in a never stamped even older o.e.m. frame...
My last big twin was a 93 FXWG. 4 engines and 6 transmissions later I got over riding it. Had the bike all of 6 months... 93 was a transition year for bearing style/supplier in the lower ends. They aren't worth the headaches.
First Shovel was a 66. Other than eating electrical parts fairly frequently it wasn't bad. Second Shovel was a 70, 3rd Shovel was a 74 (rode it once and sold it, should have been junked, it was pretty much beyond saving). Unless it is free and in perfect working order, I won't have another nose cone Shovel.
If you really want a Pan, get a 58-65, they had the best oiling of the series. S&S oil pump is a MUST, JIMS gaskets are a MUST, if it needs new barrels go S&S (there are better out there but they'll set you back a couple months rent). New heads? STD, period, nothing else comes close. Throw away the 4 speed and get a Baker 6 in a 4 (take heart meds before pricing).
If I can find one worth rebuilding, my next Harley will be a UL or VL Big Twin flattie or an XA. I've had Knuckles, Pans, both flavor Shovels, both flavors of Sportsters, K models, 45s, even had a 1920 Sport Twin (fore and aft boxer). I've has Sport Scouts, Scout Juniors and a couple 1930s Chiefs.
The flatheads are more fun. More work, more money, but lot more fun to play with.