Finally got the DNE2 overdrive installed on the C6 in my 66, had to figure out a bunch of stuff on my own. First I found a overdrive I could afford paid 500.00, then had to buy a shift motor found one at Napa for 75.00 BTW US gears wanted 198.00. Go figure. Second had to notch the cab for clearance,
Then welded a brace on the floor of the cab to keep it strong, bolted it in and had a single piece drive shaft with a slip joint out of a late model ford truck modified and replaced the warn parts. Then she was done except I had a leak and ended up pulling it and replacing the single tailpiece gasket with 2 gaskets. Then built my own relay control and added a couple of LED’s to mon the state, normal / Overdrive I was in. Was it worth it? You Bet!!!
I run 65mph at a tad over 2000 RPM and the single drive shaft is a lot smoother than the two piece. Ill try to get pic's in soon. So I now have a heavy duty 20% overdrive for less then a 1,000.00 bucks. In fact I leave it in overdrive most of the time now and use 1st and second for in town driving.
The list is finally getting shorter
pw disk brakes check, pw steering check, C6 check, 3.08 rear gears check 4 barrel and intake check, new cooling system with shroud check, and
Overdrive check.
Now it's time to get to work on the body

 

Overdrives are absolutely worth the work and cost. I put one in a CJ5 I built years ago, got it cheap because it needed some repairs, made the repair and dropped it in, Wow what a difference that made. Gas mileage went up, RPMs went down, and in the Winter, 4wd with overdrive engaged, 2nd gear would be almost like having an automatic. Mine was a warn unit and had another shifter up through the floor.

Congrats.