On the E38s (95-01')like mine is the 740 is the 4.4l v8 and the 750 is the v12. The further on in years you get the higher the number goes. The new 750's are the v8's and the 760's are the v12.
It feels pretty cool having a car that cost 65,000$ new. And I picked it up for only 500$ more than I bought the explorer for years ago. Heated seats (IN THE BACK!), heated steering wheel, power everything, power AND mpg efficiency. These cars are an absolute steal if your the kind of guy who can fix it yourself and not give money to a mechanic.
The stock stereo sucks and the speakers are crap though. And because mine has DSC audio I can't replace the stereo without replacing the stock amps as well so I'm waiting to do the whole thing. It's killing me because I'm kind of an audiophile but ill survive.