SASCO had a lot of odd parts for those cars, you might want to try
them. While I don't have a parts book covering a '58, I did get the
striker plates off the back doors of a '57-58 Scotsman at Jack's Auto
Ranch, in Watertown, WI.
http://www.jacksautoranch.com/ The bumpers
were there too. The wheels were still on a '58 Hawk when I was there
last. Hopefully they are the correct 14". They had 3-4 dozen
Studebakers in the yard, both cars and trucks. On a WI map look for
Concord. An underpass on the west side of town will take you
underneath I94. Then make a right turn, heading east a bit. Say HI
to your parents.
>> Stay informed about: parts for my 58 president