Ok....between E4FS and E4RS, the different are the follows...

(1) Rear ARM are different on FS, front both use the same arm
(2) Ball diffs F/R on FS, Ball diff R on RS and Spool on F
(3) 3 degree on RS and 6 degree C-hub on FS
(4) Single steering pod on FS and Dual on RS
(5) Upper and lower chassis different between the 2. Thicker on FS
(6) Mid pulleys are diff....same on side pulleys
(7) No bumper steer spacer on FS, 5mm on RS
(8) Steel front alum rear CDV on RS, both alum F/R CVD on foam

Can someone point out what else are different...? Other internal or chassis different between the 2?

Apparently, WOLF is probably the only place in the planet earth has FS parts and kits, not even Team Magic Base in Taiwan has 1 single parts and kits. And by adding the above parts together....buying a kit is a lot CHEAPER then upgrading/stocking the FS parts............is that correct?

Thanks everyone....