conversion help please

my CRT Truggy conversion is coming along....here is a parts list so far...
i have the RCM motor mount
in route is the Neu 1515/2.5d/f and the Monster max ESC and a couple of 46t spurs
i'm making a list now for RCM...
i was curious if it would be a good idea to run the RCM front motor cover and rear motor endbell cover i see on the site??
besides a couple of pinion gears( 11 and 13 ??) and working out the battery trays is there anything else i should be ordering that i'm missing ??
I'm pretty sure i will go 5s but can i go 4s if i want?? (this will be mainly a racer,not a basher)...any battery suggestions (i'm hoping to run a single battery set up)
thanks for any help and suggestions