US Car Tool A518 Cross member

The big thing when making that crossmember is driveline angle. Get yourself 2 spirit levels, and an angle finder. Since you will likely have to make the crossmember with the new transmission in place as a jig of sorts, you will need to do a few things.

Firstly the car needs to be dead level front to back. Figure out how high up in jacks you want/need it to be, then level it front to back using spirit levels "torpedo level" on each of the door sills. Remove the carpet sill plates and mount each level to the door sill itself. Now shim the jack stands with steel sheetmetal stock until both levels are level. Put the jack stands on the frame rails, not the suspension.

Secondly before removing the old transmission, remove the carburetor and put the angle finder right on the carb mating flange on the intake manifold and note the degrees of down angle of the drivetrain.

Thirdly, with the new transmission bolted up to the engine, you have to maintain the original down angle. Whatever angle that angle finder shows on that carb base on the intake manifold is what you should strive for when building your new mount.

You can build it where it let's the trans droop maybe 1° lower, because you can always add a shim or 2 under the rubber trans mount to bring it up a degree if you have to.

Stick a jackstand under your new transmission and shim it to get it to where the angle finder read before removal of your old transmission.

At this point build your new mount to fit the chassis, and transmission using the car and transmission as your jig.

Until you get the new mount built, do not remove the car from the jack stands or take the jack stand out from under the transmission. The car is leveled so the mount is built with the correct amount of down angle.

Now the fun begins. The 42RH and 46RH both use an A727 sliding yoke. Shorten the driveshaft accordingly.

Your stock flexplate should work just fine with the O/D trans torque converter.

If you use the 46RH which is better suited to a C body cruiser and is A727 based , PATC makes a shifter solenoid and wiring kit for this transmission making the O/D fully automatic.

I would recommend a mid 1970s Chevy pickup truck transmission mount. It fits the mopar trans with a little filing of the mount holes to oval them out.

A set of trans lines from a 1999 dodge B350 van are a direct bolt in. You will need to use a transmission cooler thermostat, and a standalone cooler. I used a cooler and thermostat made by Derale. You will need to plug the radiator cooler lines. The O/D transmission uses 3/8" lines. Your old one is 5/16" lines. This is why the stand alone thermostat, and cooler are needed.

You have 2 options on the kickdown cable. A lokar kickdown cable kit, or a homebrewed one using stock parts like I did. If you use stock parts, get a kickdown cable attach lug by Edelbrock for a chevy TH350 trans. It will allow you to connect the stock mopar kickdown cable up at the carburetor.

use your stock shifter lever off your old trans. It will fit the new one, and in the same spot. If using a column shift it shouldn't be too much of an issue hooking it up.

Hope this all helps.
Matt