I use tamiya f60 body and it looks decent. The stock body is fine also. For f60, I just had to trim the rear part to make sure nothing touched so the suspension could work properly. The wheelbase is little longer than f104 so the area between the motor and the rear wing is exposed that much more. But when the car is running you don't really notice it.
For correct tires, refer to the last few pages of this thread.
To me the must have hopup parts are
1. the upper exotek suspension arms
2. Front Lower arm reinforcements by exotek
3. Fast gear set and larger pinion.
And the upper deck is another weak area. I broke 2. Exotek carbon fiber v2 chassis is very nice to have.
IFS is not a must have item. I have one but I don't use it.
Fgx rear wheels are toed in while the solid axle, direct drive cars have no rear toe angle. Therefore, the car is more stable but that creates drag. The extra parts in the tranny also create drag and the energy is lost as noise. And you will have to be really good to beat good drivers with f104. But this car is what I ran last night for the main because my f104 broke and f1r didn't have enough steering. And I came in 3rd out of 7 cars where the other 6 were all tamiya cars I think. There are only 2 choices for the front tires and 1 option for the rear (unless you modify the wheels) where as f104 has a dozen options for tires. I just leave the soft/soft for indoor carpet and 33t pinion and the car is always ready to perform.
My challenge is to drive both types of f1 cars better. I need to learn how to set up the cars correctly and master the skills so that I can consistently be on the same number of laps as the top drivers. I have a long way to go but the fgx minimizes my frustrations when the f104 cars fail. Hahaha. I love all my f1 cars, however.
I just did re-wired and it looks cleaner.