240's and 700 series cars of the same vintage all use the same gearboxes. I'd look for an M47 transmission. It's a true five speed whereas the M46 is a four speed with an electrically operated overdrive. Just seems a bit fiddly to me. The big problem I see in using 240 parts is the other things you'll need besides the transmission like the clutch pedal assembly and such. And as I typed this, I also remembered you'll need a different driveshaft. Having a limo, this creates a problem. You only need the front section, but using a new one will throw the whole thing out of balance, and if they used a unique (longer) front section, I have no idea how to get around it. Good luck and read my other posts because I think I hit every problem possible putting an M47 in my 740.