[Justinbolin]

A Gorillamaxx G4 chassis is for the newer EMaxx trucks including the Brushless EMaxx.
The Gorillamaxx G2 chassis is for the older EMaxx trucks most notably the Emaxx model# 3906.
The Gorillamaxx G3 is also for the older EMaxx model# 3906.
The G3 is nearly the exact chassis as the G2 with a couple of exceptions.
The G3 is carbon fiber the G2 is aluminum.
The G3 has thicker (2.5mm) top and bottom chassis plates then the G2 chassis.

The G3 comes with an extended rear top plate and extended rear skid plate. That's what the 'extended G3 chassis' is referring to.
You could've bought the these pieces separately from Gorillamaxx with either a carbon fiber or aluminum extended rear top plate, or a regular sized rear top plate (no skid). The ext rear skid is always aluminum.

You can use a UE monoblock extension on any of the Gorillamaxx chassis'. You can not use the monoblock if you have the extended rear top plate and extended skid installed on the G2 and G3. You can use the monoblock on the G2 and G3 if you have the regular length rear top plate installed and whatever skidplate.

All 3 chassis' lower the center of gravity on your EMaxx once installed. These were made for racing your EMaxx and giving it more of a 1/8 Truggy stance which is better for racing then the taller stock Monster Truck stance.

The biggest difference between the G2 and G3 vs the G4 chassis is what transmission you can use on the chassis'.
On the G2 and G3 chassis' you have to use the older EMaxx 3906 transmission or a 3906 trans that's been converted to a single speed with the Gorillamaxx G1 transmission kit.
The G4 accepts the newer Traxxas transmission that comes on the Brushed/Brushless EMaxx, Brushed/Brushless Erevo and the Traxxas Summit Monster Trucks.

Hope that helps, if you have any more questions or if you need parts for your Gorillamaxx truck build let me know, more then likely I'll have the part you need, wether or not I'll sale it to you is another matter. Lol!
One last note, the Gorillamaxx G4 chassis has become one of the harder to find EMaxx chassis's out there. I have people trying to buy one of my G4's all the time.

- Justin