back in my junkyard ownership days, guys would grab a 383/440 with 727 out of a C-body, then we would cut off the mounts from the C-body K frame.
these would be bolted to the engine, then with the /6 mounts cut from whatever K the buyer was working on, the engine and transmission was lowered into the car, the mounts were tacked onto the K, engine/transmission removed, then the mounts were welded into place.
back then, nobody removed the K. just pulled the engine from the top.
crude, and far from correct, but a ton were done this way and worked out great.