Great Idea!!! I did the A518 conversion on my 65 Dodge D200. Since it's a truck there was no modifications to the floor of the truck at all. I am using the Superior transmission vacuum switch and a couple 44 and 50 psi TH 350 pressure switches for the LU/OD. I grabbed transmission lines from an a518 (3/8") as well as the detent cable and brackets. I put a Superior shift kit in as well.
Now for the fuel injection I'm doing a Holley throttle body controlled by a Megasquirt ECU. I could not go with a EFI from a Magnum motor because I have a 318 Poly in the truck with only about 68000 on it right now. So far with the A518 conversion I can get about 16-18 maximum on the highway. My engine runs at about 2100 at 70MPH with 4.10 gears in the Dana 60. It is well worth the investment! My project cost including fluid, clamps, hoses, and all the little crap was $575...nope...$455, I just sold my NP435 on Craigslist for $120. Good luck and have fun with your project!