new CC 2200 in older 4906 e-maxx, have setup questions please advise

[extremexmods]

Have an older e-maxx (3906 model) and just put a mamba monster 2200 in it. Love the power on my elite 5000 mah 7 cell packs. No need for more power this is enough for me.

1st problem: radio range sucks. Lucky to get around 75 feet of range, usually closer to 50 feet before it either stops if im lucky or glitches, lurches to a stop or slams from forward to reverse which im sure is killing the gears. I believe the issue to be 27 MHz TQ 3 radio system is no good with a brushless. Looking to upgrade to a 2.4 GHz system. Any guidance as to what I should get? I originally was thinking a spektrum system but after research I have seen a lot of stories of short range which scares me. Now im thinking the traxxas TQ-I system or a futuba 3pk system. Which would likely have better range with a brushless system? Range is most important dont really care much about extra features like multi model memory or adjustable end points. Planning to keep the 2 speed so I need the 3rd channel to operate the shifter. Any thoughts about the radios listed here? http://www.bigsquidrc.com/2-4-ghz-ra...itter-shootout
Seems traxxas had an older 2.4GHz system before the current TQ-I, how does the range compare on the new vs old? Any other radios I should look at with reasonable pricing?

Second issue: transmission idlers
http://www.unlimitedengineering.com/...ore/13407.html Is this for the 3906 e-maxx or one of the new models?

third issue: differentials: my rear differential is upgraded slightly but not shimmed. Alluminum inner drive cup with 3 mm screws vs original 2 mm screws, and alluminum outer case. Looking to shim this differential completely, (outside and inside the cup as well as the outdrive from the differential to the center drive. What size shims do I need and maybe some links that would help me. Saw a couple posts elsewhere on using rubber O-rings as well when shimming, is that really needed? If yes, where and what size?

The front differential is bone stock for the 3906 model, nothing has been done to it. Was thinking just getting a differential from ebay from a stock e maxx brushless supplied by traxxas. Would that be sufficient or do I need to do additional work?

Any other thoughts or suggestions? Thanks.

note: asked this in a different part of the forum, deleted that and moved it here, Arct1k said TRX3996X idlers from the new e-maxx would work but require either grinding the idler or the inside of the case, just my luck I would mess something up so if those UE idlers are direct fit for an older e-maxx I would take them, just need confirmation they are the right part.