Chassis Numbering

Does anyone know what the difference between the er34, hr34, and enr34 chassis are? I want to know if the frame is any different, or the a-arms are different, or whatever it is that make them distinct. Any help would be greatly appreciated. Thank you all.

So because of the lack of responses to my question, I am led to believe that there is really no one on this forum who really knows what they are taking about when it comes to Skylines.

Does anyone know what the difference between the er34, hr34, and enr34 chassis are? I want to know if the frame is any different, or the a-arms are different, or whatever it is that make them distinct. Any help would be greatly appreciated. Thank you all.
ER34 is a GTT model with RB25 DET RWD
HR34 is a GT model with RB20 DE RWD
ENR34 is a GTT-4 with RB25 DET AWD
BNR34 is the GTR34 with RB26 DETT AWD

Yeah I get that the HR is the GT and GT-V models, the ER is the GT-T and GT-X models, the ENR are the GT-FOUR and GT-X FOUR, and the BNR are the GT-R models. But that is not what I am asking. I want to know what is the difference in the frame of the car if any? Do they use different parts are is it all the same? Could a ER be made into a ENR or would you have to switch out the entire front wheel assembly?