There are 5 different model numbers of the Tmaxx. Models 4910 (which has 3 versions – the early narrow maxx with a pro.15 engine, the wide maxx with the 2.5 engine and the newer Tmaxx classic which also has the 2.5 engine).
Then there is the Model 4902 – 2.5R engine & 1st grey transmission, model 4909 - 1st 3.3 model, model 4908 extended chassis & no reverse, model 4907-extended chassis, no reverse with the 2.4ghz radio system.

A black transmission indicates it is one of the 4910 models.

It’s usually cheaper to buy a 3.3 roller and install your engine to bring it up to current 3.3 specs than buying all the parts needed to fully convert a 4910.
Eliminating reverse in the black transmission is as simple as installing the FOC (forward only conversion) for around $10.00.