I got my sc18 used but so far I have put the rc18 long shocks and ball diffs (which fixed the dogbones coming out of the outdrives issue).
And a whole bunch of LEDs so I can drive it at night.
Only other changes I want to make now is softer springs for the rear, its a little too bouncy on dirt, but it sure is enjoyable, a lot actually. And a velcro to hold the battery down, that plastic thing that comes with the car is useless, my battery flew out of my car the other day as it was doing a centuple cartwheel which it enjoys to do regularly do to my poor driving (still learning how the truck behaves on different road conditions...)
And with the long springs if I'm driving on asphalt and it veers off into grass I can just drive it off into the asphalt again, instead of it getting stuck in the grass and me having to walk all the way up to it, picking it up, and putting it back down on the ground...
Also my truck came with a maxamps 2200 mAh battery, and since you say that 1600 fits then these 2200 should definitely fit, they are shorter in length also. I have not measured the size of the battery compartment though, I am just going by your words saying a 118mm one fit, these are 114mm
2200 2s 40c
http://www.hobbyking.com/hobbyking/s...arehouse_.html
2200 2s 25c
http://www.hobbyking.com/hobbyking/s...arehouse_.html
edit: going to put some pics of the car in a bit just cause... im bored at work