3000b is faaast! and fun. You can shoot handheld LF with that stuff!
Actually my recommendation would be fp100b. Love it. Also try the colour version, fp100c. Sweet stuff. And of course, if you're just proofing, you can shoot the smaller (and less expensive) version rather than 4x5, if you wish.
I dunno about the polaroid holders, I just picked up a Fuji PA45 holder whcih is light and well made. I don't recall which previous polaroid packfilm holder is approriate but the 545 is the individual sheet film holder, right? You do not want that one. All the fuji films are pack films, not individual sheets.