I'm sure you know how to replace a car so I won't describe too much here.
Just the thing with the additional bodytextures in the tunergarage could be new for you.
so, just replace the hotring.dff and hotring.txd in the gta3.img as usual, and ADD the hotring1.txd and hotring2.txd. After that rebuild the img. Ready
For the handling,if you want a GTA:SA-like handling just leave the hotring-handling, it's quite fine.
Here is a realistic handling made by Cerbera. Many thanks to him.
Awesome work on the detailing of the car. The only thing that has me a little off is the acceleration... If I knew which number it was in the handling file and if I knew what I was doing with changing it I would. The problem I find with this car is that it's slow off the line, unlike the real life car.