1) The B4 is a software program that you install on your computer, you would use your 740 to control it. It would need a good sound card, and excellent speakers, maybe even a keybord amp setup to sound really great.
2) There is no way to make a disk from the B4 program that will run in your 740.
3) The good news is your 740 has a "Drawbar' mode that helps it recreate some of those Hammond sounds. I have a 730, the previous model, and it has some very usable Hammond sounds, especially if you play it thru a keyboard amp, or a really high power stereo system.
4) unless you want to invest in a fast computer, witha great sound card, and a really good speaker and amp system for it, plus be tied to your computer when you play, the best alternative for that "true B3 sound" is a hardware module that you connect to your 740's midi ports. VOCE makes one of the best, (VOCE V5) it sells for about a grand I think, and would require an amp, but it has real drawbars, and great Leslie simulation.
5) the other choice would be a dedicated B3 keyboard. Roland makes one, Hammond/Suzuki makes one, Oberhiem makes 2, one of them is a double manual model, that also has optional foot pedals. It is called the OB5, and retails for about $1600. I have heard that it is not quite as good as the VOCE module, but the idea of two manuals intrigues me.

Play around with your 740, I am sure you will get some B3 sounds that will satify you for a while... then you can consider the alternatives...

hope this helps,
Dave (Can't get enough of that "Hammond" sound) Waldman