Greetings, I have a couple of quick suggestions for you as I have experienced some of the items you touch on in your post. I am in the process of converting an LS1 to an LS6 and dropping it in my 1992 GMC Typhoon. Once its in I am going to turbocharge it.

I may suggest that you consider a HOLDEN FRONT SUMP oil pan. They are on ebay from time to time. Since I am working with an older generation S-series truck than you my options are a little different. However, since I am retaining the AWD I have to also deal with the front axle housing and tube assembly. The 6.0L truck pan is what I selected and have modified to use on my conversion. I am also with you on the appearance as STOCK as possible. I have uploaded almost every item I have acquired for the conversion onto my gallery (complete with GM part numbers).

If you are considering retaining the AC, you have 2 options:

#1 Chop and section the front frame for the AC compressor

#2 Acquire the bracketry from Street and Perfomance (Street and Performance) to move the ac compressor UP and out of the frames way.

Personally I dont like chopping the frame, I will tell you that Street and Performance brackets aren't cheap. The entire kit with AC Compressor is $529

As far as radiators are concerned, Jags That Run have a good idea (Jags That Run), that I will employ on my Typhoon. They take a radiator out of an 84-89 C4 and slide it under the radiator support of my generation S-10. I am not sure how much difference there is in the rad supports between our two trucks. You maybe able to employ the same thought process on yours. This will allow you to acquire and additional 4-5" of much needed room.

There is a book on ebay that addresses this very conversion as you are contemplating. The guy drops in a Z06 (LS6) motor into a '00 S-truck. IMO, he's sort of a hack but gets the job done. But I dont feel its worth the $$ he charges as its not very well written IMO.

As far as adding additional capacity, consider adding a separate cooler and a bigger oil filter, that should help SOME with your issues.

And lastly, the shameless plug for my website and gallery. If you are bored, go ahead and check out Turbo LS6 Typhoon Project and the gallery that has some pics.