Well, IMHO, if the engine block is the same, unless radical states of tune are considered, most/all components should be the same for the same model year.
Looking at the 4.0 V8, if one model declares 183 bhp, another 185 bhp and another yet 190bhp, chances are it's all in the twists and turns of the exhaust manifold and the shape/size of the air filter.
But water pump, oil filter, starter motor and other ancillaries are all the same, it's a matter of logic applied to logistics.
OK, the day I will buy myself a TVR, I'm ready to pull my hair out of frustration for hand made, one off parts, but as long as I'm within the confines of BLMC and/or JRT, I should be safe and sound.
Thanks, all !