ACTUALLY...you CAN replace the lifters without taking the heads off. How? Take the cam out, put a piece of cardboard or other firm media to act as a cradle in the cam journals of the block and with a magnet, pull the lifters down. They will be caught by the cardboard when they fall if they come off the magnet. You can replace them the same way you take them out.
It would be HIGHLY difficult, but it can be done. I would never recommend it.
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