Have a look at this site and it will provide you with further information on the 4L65E(450HP), 4L80E(1000HP) and 4L85E(1200HP) (maximum high perf or race settings).
http://www.e700r4.com/
Quote from site "#LS1-700. Crankshaft spacer to install an early type 4L60E transmission or 4L80E on a LS1 type motor. Six longer flywheel bolts included. The LS1 flywheel is reused. The flywheel goes on first then the spacer. The torque converter bolt holes in your flywheel must be elongated to fit your non-LS1 torque converter bolt circle. Cost $85.00
#10C. Crossmember for the 4L60E to 4L80E transmission conversion, 2000 up Tahoe and some others. This custom made crossmember moves the transmission mount to the correct position for the 4WD Tahoe 4L60E to 4L80E conversion. Works with the #3XX deep cast aluminum pan that holds 3 3/4 extra quarts of fluid. Cost $310.00. On some trucks the crossmember will slide to the rear. This price includes a $140.00 core charge, return your old crossmember in good undamaged condition for a refund.
#10C2. Crossmember for the 4L60E to 4L80E transmission conversion, 2000 up Tahoe and some others. This custom made crossmember moves the transmission mount to the correct position for the 4WD Tahoe 4L60E to 4L80E conversion. Must be used with a late model type pan. Cost $285.00. On some trucks the crossmember will slide to the rear. This price includes a $140.00 core charge, return your old crossmember in good undamaged condition for a refund.
#10T. You get the 4L80E to Tahoe 4L60E transfer case adapter, custom made 4L80E to 4L60E transfer case output shaft, 4L60E to 4L80E wiring adapters, LS1 motor to 4L80E crankshaft spacer and a #10C custom built 4L80E crossmember that moves the transmission mount to the correct position. You saw it here first. Even the best built 4L60E transmission in a heavy 4WD supercharged Tahoe wont last long, a built 4L80E transmission is twice as strong as a built 4L60E transmission.
Cost $1074.00 Nicely priced also with all things considered!!
