Hi guys,
A bit of an update--it's been a laborious couple days.
When I got to the decaling part, I had decided to make the Marine version--obviously, since I chose that green scheme--but when I looked at the decals, I realized that they were really just a fantasy. I couldn't find a tank in 5-6 reference books that matched the markings. Here's what they proposed:
The closest thing I could find to a Marine tank wearing "C-23" was this real tank, named "Disaster" depicted on the cover of Squadron's "M48 Patton in Action". It was from the 2nd Platoon, "C" Company, 1st Marine Tank Battalion.
You can see that there are markings on the fenders (Tamiya omits these completely), numbers on the side stowage boxes (Tamiya's numbers are incorrect) and "C-23" and a shield marking on the muffler housings, with additional lettering on the gun barrel. Tamiya gives you only the shields and one--ONLY one "C-23". And of course, you don't get the searchlight cover markings.
There's a shot of the real tank in Osprey Vanguard #29 "The M47 & M48 Patton Tank". The Squadron artists did a good job capturing all the markings.
To put it mildly, it was a b**** trying to figure out how to convincingly and accurately mark this tank. I first tried hand-painting them all--forget that; I"m simply not that talented, lol. Then I tried making stencils. Again, it looked like crap. Finally, I searched diligently through my huge collection of decal sheets a second time, and finally found two additional M48 decal sheets hiding in the bottom from two previous M48s I'd built years ago. Here I was able to do some creative cutting and painting to get what I needed.
I needed a yellow circle with a "52" on it. I couldn't find one anywhere, so I had to make one. I used a circle template to spray yellow on top of an already-yellow circle decal from a German sheet--you can see the finished one to the left of the original marking there. Then I used numbers form the sheet to the right to get my "52".
I was able to find all the "C-23"s and numbers by cutting up the old sheets. Man, this was some tedious work, lemme tell you.
I hand-painted the "Disaster" on the barrel. Here's what I have so far. NOW I can start weathering.
Stowage? We got stowage! The crew is getting painted as well...anybody see anything out of place with the colors on the gear? I'm not sure of the "correct" colors for Vietnam-era gear. I'm going by what I can ascertain from photos, so I think I'm probably close?
All comments and critiques welcomed, guys! 
P.S.---this tank saw action south-east of Danang in Feb of 1970. Does anyone have any information on what kind of soil would have been in that area? Red clay? Or something more "normal"?