318 with a 904/727 and Overdrive

Hello Mopar-Maniacs,

I have had my grandfather's 1972 Dodge Dart Swinger with original 318 and 904, I purchased from him in 2004 before he passed, sitting in a garage since 2007 when I moved out of state for work. 2016 arrives, I've moved back and looking to make some long term "strength and conditioning" performance mods other than what I've done.

Current mods to engine; 4 barrel 650 Holley, Edelbrock Performer RPM dual plane intake, a very street-able cam (can't remember exact specs, but will get them soon), Mallory High-Fire distributer, new main, rob and cam bearing (I have 75 lbs of oil cold oil pressure and 25-28 lbs at warm idle), Hooker 1 5/8" primary to 3" collector, 2 1/2 reducers to straight pipe running into Borla XR-1 racing mufflers and dumping out before the rear wheels. Sounds GREAT, very mean, but very smooth idle around 750-800 in drive at the red light.

The work is quality, but after driving it around like a teenager (Even tho in my mid 20's back then, I had a heavy foot) before I put it in the garage, the tranny is slipping a bit now. I'm sure sitting for 8 years and only starting it once a year when I would come home didn't help. I am looking to do a tranny rebuild with a different tranny and trying to decide on a 904 or a 727. Most importantly I want to eventually upgrade the rear end with higher gears, so I want to make it an O/D swap so I can still cruise and get 18-20 mpg I currently get. Here's the question...

What model/year of other small block 318 fitted car/truck transmission will bolt directly too it that has a from-factory O/D? I have a very close friend that has a performance tranny shop that can do a rebuild for me at a great price, but doesn't know Mopars, so I have been looking online to find one that will work wth my engine that doesn't need engine management system for shifting. No luck so far. Basically looking for something that has downshift linkage connections for a carb car that will bolt up with no/little modifications. Looking to grab one from a swap meet or pull it from the salvage yard.

I plan on keeping the original drivetrain and rebuilding it back to original keeping it in my garage to keep the numbers matching components. All the mods will be done on non-numbers matching hardware. Don't worry guys, It was hammered in to me by my grandfather years ago to never get rid of the original equipment.

So, does anyone know what transmission will work?! I know I may have to get a shorter driveshaft and probably some brackets to mount correctly, but want to make this first big mod something that will be strong enough to support an eventual mild engine build up to about 425hp.

Thanks in advance for the information and schooling a young Mopar fanatic in the right direction!
Author: Woodys72