I used an 07 Cadillac CTsV pan on two of my builds with factory front cross members. On my Porterbuilt chassis truck, I used a Fbody pan, I don' think anything else will work with it, but not 100% sure. With 6L80 you can also use the tranny pan from a CTsV (I can't remember the year, it's in my 68 S/C build thread). It will gain you about an 1" of clearance.
Here's an old thread on LS oil pans:
http://67-72chevytrucks.com/vboard/s...d.php?t=272174
I PM'd you my cell # if you have any more specific questions.
R