This is a really common problem with this model (and the Ford Ranger with which it shared its mechanicals). Many buyers avoid this model for this very reason. Even though many fixes have been tried it seems that this car, shown a hill and a hot day, will often overheat.

Several theories exist including that the EGR valve is the problem, as it fails and allows coolant to escape (usually into the engine cylinders). But even when the EGR valve is working properly, this engine is prone to running too hot. Some other theories hold that the thermal management of the engine itself was just underdone and there’s no real fix for it. That’s borne out by the number of people who have tried different radiators, thermostats and cooling fans and still have a vehicle that overheats.

But you could try reverse flushing the radiator and making sure than every part of the cooling system is working efficiently and properly. That will maximise your chances of not having the engine overheat but, in this case, there are no promises.

If we’re talking about the current model D-Max and BT-50, then yes, the entire driveline should be interchangeable. Under the skin, both the Mazda and Isuzu utes are the same vehicle. Car makers enter into joint ventures like the development of this pair of vehicles to keep costs down by sharing the expense of developing, engineering and testing parts like engines, transmissions and, of course, drive-shafts and CV joints.

While most joint ventures like this one will arrive at two vehicles with some visual differences and usually some details differences inside, when it comes to the oily bits, making specific driveline or suspension parts for one vehicle over the other is defeating the purpose of the joint venture in the first place.

It’s unclear from the information you have given us just what the problem is, but I can make a guess that the belt is not tightening around you when you put it on. Whatever the problem take it to your Mazda dealer and have it checked, it could be a fault with the retractor; it could be a problem with the webbing.