If I read this right, you want to replace the C6 with a NP435 and need to know what you need. First you will need the clutch linkage assembly (pedal, mounting bracket, linkage, linkage mounts, throw out fork) from a donar truck. You will need to change the fly wheel to a manual and install the pilot bearing in the crank. You will probably need to change the tranny mounts as the manual may not share the same as the auto. And then you will have to think about drive shafts, if you change the location of the transfer case (fwd or back), this will require new drive shafts.
I thought about doing the same thing till I rebuilt my C6, put a shift kit in and a heavy duty torque convertor. Plus watching my friend off road and listening to him bitch about his manual tranny and how he wanted an automatic.
