Hi - I have a 765 in a Horn Perflextion cabinet. The 765 is the same machine as the 770. The 765 was a promotion, special edition that Bernina had where the machine has a rose colored front and came with your choice of the Bernina 330 sewing machine, an embroidery module or a quilters package with BSR. I think the 770 comes with the BSR and quilting/patchwork feet. That is the only difference between the 765 and 770. I'm sorry I don't know about the 740.
I have the machine in a horn Perfexion cabinet that is the same specs as the Horn 3280 and have had no problems with it. The Perfexion cabinets were a knock off of the Horn cabinets, but made by Horn. I bought it at Sew Vac Direct, but I do't think they make them anymore. Anyway, in the photos it looks exactly like the 3280 and the specs are the same. The lift is not electric, its manual, but there is no problem with the height or opening (which is 12 1/2"' X 24")
Hope this helps!