Great thread here guys! I gotta chime again.....as you and I have chatted some already.....it's your truck, you can set it up the way you want and it will still be right. Unless you are going full bore and making an exact replica truck (and you are not), it won't be wrong. Currently you have some markings on it as an artillery battery truck. As a "gun bunny" I can tell you with plenty of certainty that we def. had lots of rolling stock, some dedicated to the gun line for carrying ammo. and powder and those "projos" had to be trucked in. Our advance party when it went out because we had a "CSMO" was a small "recon" type element used to locate, establish and hold a new position for the battery which would come later, sometimes days later. Those guys were as heavily armed as we could send them as they were going alone in a handful of vehicles. We had a couple of trucks that we mounted a .50 into the bed on a platform kinda like others have mentioned, also a couple of M60's.
Just to stick up for the arty guys, I like the artillery unit story (yes, I am biased), I also wouldn't change the whole hood and bumper numbers, I'd just take off the "04P" and put a "1" where the "P" is and call it good, as that gives you the right sequence of numbers and it still jives with what you found engraved. As far as radio's go, in my trucks I have mostly PRC 77's, again in my world "good enough". My single vehicle mount radio is an earlier version than the ones posted above, but still period correct, especially for Marines who often use old gear. Plus, on a backpack rig, I can hang a 77 on my Mule, looks cool with the long antenna.
Also as I sit here musing.....one thing that keeps entering my brain housing group is that in the "green machine", much of the gear we had was "specific" to a certain job, while a lot of other stuff was used for any and every job you (or maybe a Gunny) could think of. I never remembered thinking that we had too much of anything good, especially not too many vehicles. A big truck not only carried troops, but it also carried ammo., it also was a prime mover for a howitzer, it also made a chow run sometimes, also carried trash and maybe wounded and pulled a variety of trailers. So making something "too dedicated" to a single purpose would limit its overall usefulness for other things it could be used for. (I'm not trying to preach to the choir, just thinking out loud).
Anyway........great truck, great project, looking forward to hearing and seeing what you decide.
Semper Fi !