I'm just finishing up my swap and heres some extremely helpful info I've figured out.
The S & P style mounts move the motor about 1.125" forward in the engine bay. This makes you need new driveshafts, trans lines, relocate trans mount and all that fun stuff.
If you take the S&P mounts, move the 3 holes for the SBC engine mount 1" back (not enough clearance between holes to move them 1.125"), it puts the LSx motor in the same spot as the SBC motor. Then if you are using your original trans and t-case if 4wd, you use your old driveshafts without cutting them. If you use a new trans or transfer case, you use your old driveshaft with a yoke from a NBS truck, and if you are using a new t-case also, then you use a complete front driveshaft from a NBS with the same t-case and it all bolts in perfectly.
This also allows you to keep the trans mount brace in the stock location without moving it at all. My trans lines also fit without bending them or tweaking them at all.
For the radiator, use NBS upper and lower radiator hoses. Should fit with no problems at all.
Motor mount adaptor reference:
http://matt.undiagnosed.org/ls1/images/eng...mount_plate.jpg
That is a normal S&P style adaptor plate, to put the motor in the stock location, you move the 3 holes for the SBC mount to the LEFT in that drawing.
Old: 1998 K1500 White ext cab stepside, vortec 350. Stock besides Volant intake.
New: 1998 K1500 with stock LS2 besides LQ9 truck intake and 8.1L Marine injectors. Dynotuned, 350rwhp, custom 3.5" exhaust, '02 F-Body Racetronix fuel pump setup. All wiring, exhaust, motor brackets done in shop.