Looking for Overdrive 4spd Aluminum Transmission

For me I am done with trying to mash gears and drag my 340 up to 7000rpm. I just want to get on the highway and cruise my Dart at 70-75mph and still have some low end. I have a mild 340 with 484/284 M cam, aluminum heads, RPM manifold, fuel injected factory 4spd car. swapped the 4.10 to a 3.23 and at 2800rpm I'm doing 63 mph, I run 275/50/15's. Yes a 3.55 gear would be great with this set up and cruising the hood but I want to actually put some miles on it. Now the modern 5spds can fix this but I am not will to cut out a 4spd tunnel to replace it with an auto tunnel so I can put a hole in the floor for the modern shifter. GearVendors option; I am not interested in a tail shaft swap along with shimming the trans angle down to clear floorboards and beat room in the tunnel for the unit. So for me and my wishes for the car I have owned for 23 years I am willing to try a OD 833 and see how it goes down the road. IMO, the biggest mistake people make when playing with their car is not being realistic to what they plan to do with it.