well my situation was a lil different i went from a world castings 454 small block to a 8:71 blown 383 small block to my 415 ls motor. ive been helping capt kllm and we learned a lot about the 6 liter motors. best bang for the buck in a v8. capt cammed his it did well then it got stolen he then turned another lq9 into a 415 with the cnc heads cam stoker and cbm got 600 hp out of it. the ls is a fantastic motor superior to the sbc in every way. yes the head and cam combo is worth the dollars.
also there are 2 types of heads out there for the 6.0 you have the large square port heads from the ls7 and ls3 and ls9 and then you have the cathedral heads smaller ports from the 5.3, ls1,lq9 and ls2 capt running cnc cathedrals and making about 600 hp < but he also is stroked, i would discuss it with bruce and chris @ cbm. and both style heads have to run there respective intakes. they dont interchange.
remember these are air pumps flow is the name of the game. the more air you flow the faster you go !!
i dont know how much hp your looking for. or tranny or cvs you have it all plays together.
mike, i would def look into a pbs tranny for your car it goes into the same basic space as your 2d but it uses the bigger s4 type internals. however there is lots of folks running 2ds behind 500 hp but the more wheelies and jumps and fast runs through the dunes the stronger your tranny needs to be ( but you know this already)