the 18 SS+ kit has more top end because it comes with a 49 tooth spur where the g3.0 has a 52 tooth spur. 49/15 in the kit should be fast enough for most but I prefer 52/14 for smaller spaces and better acceleration. 52/15 is the stock g3.0 gearing.

the kit version engine is a standard threaded crank so it uses a pilot shaft adaptor instead of the g3.0 engine set up because the g3.0 engine is a pilot shaft engine, not standard crank. I dont know why they did this between two mostly otherwise similar cars.

the g3.0 engine mount is actually better because it is a one piece design and offers more solid support. the kit uses two purple mount pieces on each side of the engine that are not connected. when I tried to put the g3.0 mount on my OS 18 CV RX it would not fit because of the pull start so I had to use the kit engine mounts (as well as the pilot shaft adaptor because that OS engine is a standard crank). (i didnt build my SS+ kit yet so its without a few parts for now)

also the kit comes with pin tires so if you get that you may want to get some dirt hawg/geolander tires for pavement use to not wear the pins down when not on dirt.