Putting the m41 is a bit more than an all day project, but not horrendous. I opened the floor to the necessary width, (after measuring things a zillion times) with a sawzall. I then took a piece of two inch angle iron, 1/8 thick and laid it parallel to the opening and welded it into place. This allowed me to have something to attach the new tunnel cover on to.In a sense, it looks like an upside down rural mailbox. By doing this, I can remove the cover and access what is underneath. As for the drivelines. I am told you can mix and match with 122 automatics. I live in north Idaho. No one even knows what an Amazon is, let alone have one laying around for parts. I went to the driveline shop. I chose to use the short shifter and it is a perfect combination. I have a couple of pictures, but could get some more if you are interested. Email me and I'll give you some details. I don't know what year your 544 is, but it could be more difficult if it didn't come with the b18 to begin with.

Leonard