S.A.W, i also use the SP speedo's and motors (V3's) The LPF would be sufficiant for 2WD. I use the GT but that was only because i wanted it to match the one in my 4WD ( incase it went wrong, i could swop between the 2 cars )
Motors, i use the 6.5 in my 4wd plenty quick enough for me. 2WD 7.5 or 8.5 dependent on track. Hope this helps