I do not know if the heat shield is necessary on 47-55 trucks (on the lower side of the bed/floor on a pickup, panel, canopy, suburban, or any model with wood above the "hump" in the tailpipe); however, the heat shield was most likely standard equipment on these trucks.
I say "most likely" because I never saw a factory-fresh truck; however, the two 1/2 ton A-D trucks that I bought in the late 60s-early-70s both had a heat shield.
I think that Mar-K (and maybe others) is now selling a stainless steel version of the heat shield.
There has been no heat shield under the varnished bed boards on my dual-exhaust'54 pickup for about 7 years - I see no problems. However, I am taking no chances with my suburban - I replaced the old (? original) heat-shield with a POR-painted new one.
Tim
