Flexplate can be purchased from the dealer or from a 2500/3500 truck
Spacer--what for? Just get the correct flexplate.
VSS pigtail can be rewired. There are a few wiring diagrams on this site where you can pin the PCM and repin the passenger side connector.
Oh, and you need to know someone who can do an 80e overlay on the tune in HPT.
2000 ECSB 6.0L
TORQUER V2 CAM ● COMP 918's ● 7.4 HARDENED PUSHRODS ● K&N SERIES 77 CAI ● 80mm BBK ●PACESETTER LT HEADERS AND 3'' ORY ● SUPER 40 FLOW ● 3000 STALL ● 4.10s ● BUILT 80e ● VORTEC PERFORMANCE TUNE ● MSD 8.5mm PLUG WIRES● ELEC. CUTOUT ● UD & ALT PULLEYS ● FLEX-A-LITE E-FANS ● 22" CENTERLINE STINGRAY III's ● LUND FIBERGLASS TONNEAU ● 2" LEVELING SHACKLES ● 12K HID LOWS & FOGS ● LEDs ● DEBADGED ● WHITE-FACED ESCALADE GAUGES ● KICKER 450.1 ● 2-CVR 10's ● DS60's ● K693's