Here is what I can do Louis...
I can build a 15cwt (Chevy 1311x3) or 30cwt (Chevy 1533x2 and WB or Ford F30) with MGs, say the Lewis Gun and the Vickers Maxim, both with single or dual guns (common practice then). They also used the Besa and Lighter Vickers .30 caliber. This depended on what they had laying around or could acquire.
The Vickers Maxim and other rear pedistal MGs had full 360 degrees rotate with about 32 degrees of elevation mounted on the back. The Lewis would be mounted on a base on the left front for the passenger (right hand drive vehicle). The front MG would rotate about -15 to 15 degrees side to side with about -5 to 15 elevation.
I can make anything tow a gun. The trade off is the Unit can be tasked to attack, but it cannot entrench. The unit would be defined as a type = trn_carrier or trn_support. The key is the type 'trn' which defines truck and tow capable.
(Prime movers, even tracked would be defined a trn_tractor, like the TRV and the M5 high speed tractor. They can do anything a tank or armor unit can do, but cannot entrench. Only tanks, spgs and artillery can entrench, but cannot tow a gun).
I can replece the Vickers MG (portee) with a 29mm Breda or the 37mm Bofors with full 360 degrees rotate and elevation of about 25 degrees.
I can make the elevation exceed 25 degrees but it looks weird when the gunners slide below the bed of the truck. The Breda Truck only had about 25 degrees and the Bofors was only about 22 degrees. Since I most likely will use the same pedistal base (turret) and gun carriage, the differences isn't that much.
I'm working on several portee vehicles at the moment since the gun mount and guns were used on many vehicles. GMC CCKW, GMC M3 Halftrack, Bedford MW, Dodge WC(51, 52 62, 63), and the LRDG vehicles.
In the case of the Chevy 1533x2 30cwt, when they mounted a Bofors or Breda on the rear, it was called the Scorpion Tail, and was the last truck in the line or the rear vehicle. The purpose was to provide a gun was capable of fending off pursueing enemy vehicles. Kind of the rear guard. In these cases, the gun, did not have full rotation on the pedistal or base. They usually had about -15 to 15 degrees side to side and traverse (elevation) of about -5 to 15 degrees.
Remember, these were highly mobile vehicles that were capable of crossing deserts quickly. If they tried to shoot the guns with full rotation, the driver and front gunner would have to deal with the concusion of the 20mm or 37mm from behind them if the gun was shooting forward.
Of course some portees were designed to have full rotate, but the intent was they were stationary while firing the gun. The driver became one of the gun crewman.
If you remember the old program RAT PATROL... it was based on the LRDG. But the LRDG didn't have the Willy's Jeep until 1943, and the Desert War was mostly over by then. The LRDG was reassigned to other theaters as the war continued and served until May 1945. They were not assigned to the Pacific War but their influence no doubt did inspire many independant groups.
The LRDG was not so much an attack force, but more of a RECON force. But they did have their fights. They depended on a variety of vehicles including whatever they could pilfer from the enemy; mostly the Italians in the case of the FIAT trucks which were used for headquarters and command carriers. The FIATs were not as useable as the Chevy and Fords and even Jeeps.
The LRGD didn't typically tow guns with the Chevys and Fords. But they did tow guns on their Befords and Heavy trucks. This was usually captured guns that they would later mount on a vehicle. Remember, they really didn't stand and fight but were more of a rapid raiding force when they must fight. Because they were so mobile... they just hit and ran and nothing could keep up with them. Rommel was known for stating that the LRDG did more damage to his forces that any other single unit.
If you think a vehicle is needed... let me know. Once I have the base vehicles complete, I can add the 20mm Breda, the 37mm Bofors or a bigger gun if you wish. I have a 90mm M2 AA which was used on the M7 Preist, but in reality, it would have flipped the Chevys over. This didn't keep any industrious group from trying to maximize their firepower though. There were many accounts of crews placing anything they could on trucks to give them an edge. This wasn't any different than the M13, M14, M15 and M16 based on the M3 halftrack, all AAV (Anti-Aircraft Vehicles).
It was common to see the 37mm Bofors, 57mm, 75mm, 76mm and 90mm on a variety of trucks. They understood that these "gun trucks" could be moved around quicker than any towed gun. Many times, these vehicles were defined as Tank Destroyers, like the T48 57mm or the M3 75mm. Some were defined as Mobile Howitzers like the T30 75mm and the T19 105mm.
Anyway... I plan to add the Chevys and Fords that were the most common. So you guys building Africa and Desert maps can focus on the LRDG once these are completed.