Good Day, I have 99 Burb and it has an all original "F" code 506, no problems yet but, we all know how that goes. I bought a 94 "S" code 599 long block from SCRUFFYDOGTOO yesterday with low miles and in great conditon as insurance for the future. I know the "S" heads that came with the 599 have smaller pre-chambers than my 506 "F" block, plus my ECM is programed for an "F" Block but, Can I build up the 599 for use as an "F" code engine except use "S" code heads????? I know I will lose some power and torque but will it work with the "F" code ECM in my truck.... Of course I will use the "F" intake (no EGR) and all the good cooling stuff from the 99. Also the 599 is set up for an electronic IP. Oh yeah the oil cooling lines will need to be modified also. Thanks Guys!!!

Your ECM has no idea what block or heads it's controlling. Only difference between F and S heads is pre-cups anyways. As long as you keep your F programming, I doubt you'll loose much output at all.

Thanks RCpullerdude, figured the little extra fuel that the ECM commanded would not amount to much. Thank you for the warm tummy!

Also noticed that the two different style heads uses the same injectors which mades me feel pretty confident that it will work fine.

AFAIK, all 6.5 truck engines use the same head. Only difference is pre-cup.

AFAIK, all 6.5 truck engines use the same head. Only difference is pre-cup.
What he said

If you go so far as to have those "S" heads looked over at a machine shop, they could easily swap the pre-cups out for some "F" cups.

There are several size pre-cups for the 6.5L, as they changed periodically over the years. The Page has a nice article about them...

Thanks 93 Burritto, that was the info I was looking for. Figured it was a pretty easy R&R to change out the cups. I will now start searching for the cup articles you mentioned. Thanks!!