The Tee shirt shop you mention in Phoenix was Arizona Sport Shirts . Karl moved his operation to Indy in 1988.
The reason shirts are printed heavier is the printing ink used during 80s and early 90 had some health issue for the people printing .Yes shirts need to have Drivers Names in bold letters on from .Large Car Numbers on back with sponsors names.
You have seen me across Midwest selling GOT DIRT ? Theses shirts are done on the same printer station that McSpadden shirts were printed.See y'll at the races !!!