Re: Can you upgrade a 4 cyl to a 6?
Engine, transmission, engine/trans wiring harness, PCM, Y-pipe, probably a few incidentals like power steering and A/C hoses, possibly more. If you go to a 4.0L and drive aggressively, a swap to an 8.8 rear axle would be good.
I would stay with the same 98 year for the V6 donor parts. 99+ V6's have PATS w/chipped keys. 97-back have other electrical differences.
2003 FX4 Level II, Supercharged 5.0L V8, Headers, Duals
BW4406 manual transfer case, Aussie Locker, Torsen L/S, 4.10's
Bilstein 7100 rezzies, Cadillac/Mustang rear discs, Duff traction bars
Keypad Entry, Lock LEDs, ABS switch, sway bar discos
Heated seats, Explorer EATC, Trip Computer and consoles
2003 XLT 2.3L M5OD-R1 reg cab beater, 2011 Taurus SEL, 2016 C-MAX Energi Plug-in Hybrid