So you are saying if you put in a RB26DETT in a GTS-T, the engine becomes lighter in weight?
If so, how does putting the same engine in a different car make it lighter?
With a RB26DETT in a GTS-T, the balance will be totally different.
What difference will it make if you are both running a RB26DETT and light weight both.
The GTR is AWD to reduce understeer, FWD gives you understeer.
Hence why the AWD system will give you better traction.
Aero parts are good for stability and only to a certain point.
ie. A GT Wing Spoiler.
If the wing is angled at the correct spot, it will improves aerodynamic performance at high speed.
To increase drag or generate down force, helps stabilise the rear of the car = More control = Faster you go.
The angle of attack of the wing on some cars can be adjusted to increase downward force over the rear wheels, but it has the dual result of increasing drag.
Too much drag = Slow you down.
The R32 GTR's Advanced Total Traction Engineering System for All-Terrain (ATTESA 4WD) design is still used today on the R35 GTR but with further updates.
So the basis of the system still exsist.
Whatever characteristics you prefer is what is more fun to you and all cars cost money.
JGTC's are RWD because that is part of the Rules and Regulations.
A JGTC is not based on a GTS-T.