Need someones help.

[Patrick]

Todd was talking about the XL motors Serum:005:

Yes Todd the XL motors should work (I have a 7XL in my E-maxx).
The 540 c motors in your link have a built in heatsink so you can't put an extra one on them.
The smooth can ones (like mine)
http://www.rc-monster.com/proddetail...o5408xl&cat=20 (I couldn't find the 7XL) are the same motor with a different can. The smooth can ones will fit a heatsink/clamp on them. http://www.rc-monster.com/proddetail...d=RCM01&cat=20
And yes the XL size heatsink/clamp will fit the XL smooth cans.(an L size one will fit as well,it just won't cover the full length)
I have heard that the 540 C motors (finned ones) can hit the transmission, limiting spur/pinion combos, but I'm not sure.
If you get a smooth can XL get the heatsink/clamp as well.
If you want speed on 12 cells nimh, get the 7XL (I use mine on 14cells). For a bit less speed and bit more run time get the 8XL. 9XL would be a bit too slow I think, but you will get better runtimes.

I have no experience with the Mamba Max, but I heard it works well (if you use a UBEC).

If your staying nimh, IB4200's are some of the best ones.
With my 7XL I haven't noticed any difference in run time compared to stock, I've never timed it though.