M170 Bumper number help

[txdodge43man]

I picked up a M170 a few weeks ago and my brother has started striping the fire department red off. We have located the original hood numbers (US ARMY 1H3935) and I found the original unit numbers on the rear bumper.
The problem I am having is the driver side unit numbers make no since to me see picture I think they read on of two ways
71-BG-A3
37 SP 4
or
74 BG- A3
3/SP 1

Now I found the vehicle number no problem B 19

Any help figuring out these number would be great

thanks

 

[rdsar2k]

I think most 1955 Army M170's hood numbers began with 1A83_ _ Six letter/number total. Most I have researched had this series.Looks very close to what you uncovered. No idea on the bumperettes.