I don't know if that would work (emissions, etc) but I stuffed an L28 with 5-speed into a '71 Mercedes 230 sedan -- commuted in it about 12 years before selling. (Gal wrecked it!) It made an okay car a real fun ride, esp as it was SB42 smog-inspection exempt. Used a Maxima oil pan and throttle linkage, and notched the front cross-member (with heavy internal stiffening) but not many other changes, despite the fact that the M-B was an automatic car; very nice driver and cheap!! Shamed a Subaru WRX coupe through three gears; young dudes said "Whoa; fast car, grandpa!" Got me through my Z-less period after Nissan bought my orig owner '70 back in '95. Built a better '71 and got the silver color I ordered in the first place but settled for green...
I wrote an tongue-in-cheek article on it for Z Car Magazine (I was Restoration Editor then) but it folded (not my fault, I always hope!) before it got in print.
Red NL320 has been crowded out of the garage now; it needs a new home; $8,995.00 asking.