You'll have a lot of conversions to do but the Red Ram (I had a '54 with the 241 Hemi) and it later became the A engine. Now, this is NOT the LA. Those came out in '67. The Red Ram used a different motor mount set up. The front mount was a brace under the water pump. There were no side mounts like later motor mounts. I seem to remember that you could converter the ignition with a 340 distributor. I think it needed minor machining. I don't remember if the Powerflite transmission uses the same bolt pattern to the back of the engine. My '54 Coronet would run 80 easily once I went with radial tires and newer style rims.
You will need to fab up motor mounts, use a Powerflite or an adapter if the Torqeflite won't bolt up. The '54 was before pushbutton shifting. That came out after the suicide spear shifter on the '55 models. Somewhere I have a Mopar tech book that details ways to use the old "Whale" Hemi's. Now, I'm assuming you are using a dodge engine. Chrysler and DeSoto Hemis were different engines. Plymouth didn't get a Hemi until the "Elephant" engines came out as race parts in '64 and options in '65.
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