Yes, you do. You need the frame, front suspension, & hood from the AMT Kenworth W925 kit, you'll need the cab, interior, & sleeper from the Revell of Germany Kenworth W900 or T900 kit, you'll need to get a tandem torsion bar suspension from Eric over at P&P Resin Works (unless the AMT kit you're using already has one), you'll need the Auslowe Cummins VT903 engine, and you'll need to get the "Movin' On" decal set from Jbot. That should about do it for the series truck. For the pilot "In Tandem" truck you won't need the cab & sleeper from the Revell of Germany kit or the VT903.
Yes, I've been planning this build for a LONG time.