check this site! http://www.hpsalvage.com/ Click on project cars on the left blue box. Then look at '99 Camaro LS1/4L60E in a 98 C1500 the second one from the top. If you look at "more photos" and you will see how the frame is notched. I bought my drivetrain setup from Mark at HPSalvage. Mine and Farmtruk's rides are on that page!
2006 Superior Blue Trailblazer SS AWD, Stock as a rock
Sold: 2002 GMC Sportside Denali front end with a 2002 LS1, FLT level 5, Yank 2600, Trick Turbo, T76, Nelson intercooler, 60LB injectors, Warbro fuel pump, Eaton locker, Magnaflow, 3.42, Nelson Performance Tuning (speed density).
Sold: 1981 GMC LB RC 1500 2002 4.8L 4L60E 12 bolt 3.73 Richmond Lock Right AC PS Nelson Performance tuning