Sorry we didn't answer your question in your previous post:
https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/1380689/1958-gmc-rims.html#Post1380689

Working backwards.
Original 1958 GMC had hubcaps.
The 1958 GMC rim had clips to hold the hubcap.
Beginning around 1962, rims have nubs instead of clips (old design...hubcaps becoming airborne).
Old style hubcaps do not fit 1962 and newer rims.
Rims designed for radial tires began around 1965.
Front disc brakes for Chevrolet light trucks began around 1971.
Begin your search for 1971 onwards.

http://www.boltpatternfitment.com

If you have the $$$ there are companies that can widen orignal rims and weld-in new style beads for radials.
Attachments
1958 Hubcaps.jpg (87.36 KB, 99 downloads)

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."