Why not contact someone in the Keystone Region Chapter. You's are right in the middle of a lot of Studebaker owners. I'm sure they would be glad to help...
https://sdc.cornerstonereg.com/Chapter/ViewChapters?loc=PA
Yah, most radials I've used ( Michelin) have a 44 psi cold limit. Due to the weight distribution ratio, It would make a lot of sense to bump in front. I'd try 38 or so, for starters
I found a few things .... Mostly Imports and an occasional Stude. I guess he lucked out and had someone order the Avanti..
http://studebaker-info.org/Dealers/CAdealers.html#massagliCA
I wonder how the sides were secured. The lack of a bolt there, would chance them to bounce and scratch the paint.. Any more pics or is the Ebay thing still active?
......aha just saw it... ( rear end bump protection/projection) but the question remains...