It sounds like GM used a Mustang dyno in 99, and a Dynojet in 00.

 

1999 truck engines

Power ratings for the 4800 V8 engine:

255 horsepower at 5200 rpm
285 lb.-ft. of torque at 4000 rpm.
Power ratings for the 5300 V8 engine:

265 horsepower at 5000 rpm
320 lb.-ft. of torque at 4000 rpm.
Power ratings for the 6000 V8 engine:

300 horsepower at 4800 rpm
355 lb.-ft. of torque at 4000 rpm.


2000 truck engine outputs
NEW POWER RATINGS FOR THE VORTEC 4800 V8 ENGINE:

270 horsepower at 5200 rpm
285 lb.-ft. of torque at 4000 rpm.
NEW POWER RATINGS FOR THE VORTEC 5300 V8 ENGINE:

285 horsepower at 5200 rpm
325 lb.-ft. of torque at 4000 rpm.
POWER RATINGS FOR THE VORTEC 6000 V8 ENGINE:

300 horsepower at 4800 rpm
355 lb.-ft. of torque at 4000 rpm.

peace
Hog

 

I put my 02 injectors on a friends 99 with no problems. A LOT of the power difference is in the tune. Changing only the tune to an 02 tune will show an improvement.

 

Early 4.8's had shitty iron heads too.

 

Haven't seen one of those.....I have a 99 4.8L in my garage with alum heads.

 

the only ls series engines that i'm aware of that had iron heads are the first 6.0l's.

 

Because they're the only ones. They also had the longer crank flange making them useless to most swaps

 

Not useless if you use a 4L80E or an older style (th350/400/glide) trans.

 

Or a custom torque converter...I believe that MPFD went this route