Bellhousing: Either Lakewood (if you plan to go 11's or better) or a Tremec Aluminum bellhousing (cheaper, easier to install).
Shifter: 3550/TKO have a specific shifter
Crossmember: Tremec and/or D&D Performance sells a crossmember mod for the 3550/TKO.
Your stock clutch will work, and your stock driveshaft will probably be ok too. I highly recommend calling Joe at D&D for parts and questions - those guys are top notch.