The Sensors are added using either the ThingMaker or ShipMaker. You can pick the various sensors from the equipment list and add them to a vehicle instead of making a sensor with ThingMaker every time you need a basic sensor or communicator for that matter.
Weapons can be made using with GunMaker or ShipMaker again. The Thing to remember about the weapons constructed through GunMaker is that they do 1/10th damage to spaceships, although this isn't clearly stated anywhere it is mentioned in a few places.
I have converted almost all the vehicles from previous sources and i have used both ShipMaker weapons and GunMaker to make tank guns for example and while the ShipMaker weapon only does 1d damage that would presumably be x10 against vehicles and personnel. While Using GunMaker to get weapons up to 10d takes a lot of work.
Before I write a detailed response, I just want to make sure that I understand you correctly.
You are saying that for something like a air-warning radar for a World War 2 Tech Level ship, I need to go to either Shipmaker, by which I assume you mean the Starship Design Sequence, or Thingmaker, then either design something from scratch or choose a pre-made design. As World War 2 could be viewed as either Tech Level 5 or Tech Level 6, and Radar appears to be defined as a Tech Level 9 standard, this might be a slight problem.
As for tank and surface ship weapons, I either make them somehow in Gunmaker, or figure out what is meant by "Slugthrower" in the Starship Design Sequence. That does not answer the question regarding aircraft, and how many weapons or weapon mounts that they may have. For that matter, does the One Hardpoint per 100 Traveller dTons apply to surface ships as well as Starships and Spaceships? Does that also mean that the 1 Ton required for a turret mount, regardless of whether it is a single or quadruple mount, also holds true regardless of the size of weapon in the turret?
Just a couple of samples for the curious.
Radar appears to have a standard Tech Level of 9 in both the Starship Design Sequence and also Thingmaker, see page 635 in T5.0.9.
The AN/APS-6 3 cm Radar was a widely used US Navy night-fighter radar in World War 2. It was operated by the pilot of the aircraft, primarily single seat F6F Hellcat and F7F Tigercat fighters. It weighed 242 pounds, without including the power cables. The maximum reliable range on bombers at 10,000 feet was 10,000 yd. or 9.144 kilometers, on fighters at 8,000 feet the range was 8,000 yd. or 7.3152 Kilometers, with a detection range of Battleships on the surface of 35 miles (that would be nautical miles or 64.82 Kilometers). As of 1 August 1945, the US Navy had received 2161 at a unit cost per set of $10,938. That was a pretty high cost in World War 2, as a Jeep cost about $1000, a DUKW nearly $6000, and a P-40 in 1944 was costing $44.892. Now, does this qualify as an Experimental Set, based on the Standard Tech Level for Radar of 9?
The ShipMaker weapons when downgraded to World Scale tend to weigh in at around 500kg or 1/2 a ton easily fitting into a vehicle turret or the vehicle option of weapon mount.
Now, as you gave a weight for Shipmaker weapons downgraded to World Scale, I thought that I would post some Real World weapon weights for tank-mounted guns.
The US 37MM Gun M6, was carried by US Light Tanks M3 series and M5 series, along with the M3 series of Medium Tanks. The weight of the gun and mount was 700 pounds, or 317.7 kilograms. The Armor-Piercing projectile weighed 1.92 pounds, or less than 1 kilogram.
The Japanese Type 1 (1941) 47MM tank gun weighed 904 pounds or 410 kilograms. The Armor-Piercing projectile for the gun weighed 3.37 pounds or 1.53 kilograms.
The US 75MM Gun M3, used on the later M3 series Medium Tanks and the M4 series until replaced by the 3 inch/76MM gun, weighed with mount 1,763 pounds or 800 kilograms. The Armor-Piercing projectile for the gun weighed 14.92 pounds or 6.77 kilograms.
The US 90MM Gun M3, carried by the M36 Tank Destroyer and the M26 Pershing tank, weighed 2,290 pounds or 1,038 kilograms, but that does not include the weight of the gun mount, just the gun itself. The two principal Armor-Piercing projectiles used weighed 23.4 and 24.06 pounds, or about 10.9 kilograms.
Based on your stated weight of about 500 kilograms, the gun apparently is around 50MM to 57MM caliber, with a projectile of between 4.5 to 6 pounds in weight. The German 50MM Pak 38 Anti-tank gun, firing a 4.54 Armor-Piercing Capped projectile, could penetrate 2.4 inch/60MM of good-quality rolled homogenous armor plate at a 90% angle of impact. That would give the round the ability to penetrate an Armor Value of 420, based on the Armor Value of one centimeter of steel being 70, as given on page 640.
If you wish the specific sources of any of my data, just ask. Most if it is available online, but some is not.