I JUST did this swap...well, similar. E4)D to ZF
What I found was this.....
The top two bolts on the bell housing were too long by about 1/2". Shorten them or get new ones...they are cheap, use grade 8 bolts though.
The bolts that hold the flexplate to the crank are also the wrong length. They need to be 3/4" longer to use a DMF setup. I am not sure on a SMF setup, but I would think it would be the same situation.
I used a factory DMF from a 1990 (I think 1990) 5 speed truck. It works fine, but it is getting lucky modded when I do the turbo treatment to my spare motor and install it this spring/summer.
BENCH BLEED THE PEDALS AND MASTER BEFORE YOU INSTALL IT!!! If it's not already bled and full, or you will have a HELL of a time with it.
If you don't have the clip to hold the clutch rod back in the slave, do yourself a favor and grind about 1/8" of an inch off each end WHILE KEEPING THE ROUNDED SHAPE ON IT!!!! This made life SO much easier when it came time to put the slave in place.
Pull the carpet back and unbolt the plate on the floor....find a truck with a 5 speed and take that plate out and put it in your truck. It's much easier than trying to measure anc cut the proper size hole in your existing floor.
What I did to install the clutch was buy an extra 2 flywheel bolts that are 1 1/2" longer than what you need. Cut the heads off and thread them into the crank a little ways. These will act as dowels to slide the flywheel on (it's HEAVY) and allow you to thread the preoper size bolts in with BLUE loctite on them. Once the rest are in, remove your dowels and replace with the other two proper bolts. Torque these to 47 ft. lbs.
The pressure plate is a PITA to get right with the clutch disc if you don't have the proper tool. I just installed it loosely, and slid the transmission in place...then once the bellhousing bolts were in, I went back and tightened up the flywheel bolts (20 ft. lbs.). Blue loctite here as well!
RTV or gasket between the transmission and transer case. This keeps crap and water out of there. Ignore this if your truck is 2WD. (looks like 4x4 from your pic, I think I see front locking hubs)
Once you get this far, the rest of the truck goes together pretty fast.
I had a custom rear shaft made, but I need to get the front shaft shortened. This mightnot apply to you, as the C6 and Zf are close to the same length IIRC.
My pedals come fron a 1996, and my truck was a 1992. I am not sure of compatibility of older trucks and new trucks firewalls and pedal fitments.
A gasser crossmember SHOULD work, as I would think that driveline angles on gassers are the same as diesels.
Your starter will work, you don't even have to take it off.
Also, this is the time to fix a rear main if it is leaking, or any other little leaks. Also, take apart the connections on your GPR and clean them, dielectric grease and put it back together.
WATCH YOUR HEAD UNDER THERE!!! There are tiny screws that poke through the floor that are waiting to stick in your head...watch yourself under there!!!!
Other than that it's a piece of cake. Goodluck and if you need any help, shoot us a reply on here and we will do our best to help. You are going to LOVE that stick behind that diesel...it made my truck REALLY come to life!!!