I actually have an RCR cooked up to further clarify 6.14. The intent of 6.14 is to allow GenIII 5.3 engines which is why the RPOs are called out. LM7 is the basic bitch iron block, L59 is flex fuel, LM4 is aluminum block from Trailblazers and Envoys, and the L33 is special. The first 3 all have the small cam and LS1 based heads and lower compression. L33 has 9.9:1 compression, LS6 based heads, and a higher lift cam.

We do need an RCR for the 5.3 in the 3rd gen, apparently the truck accessories work better in it than the 4th gen car stuff.