The "assembly" that Baileys sold was a little misleading, it consisted of the shroud which you wont need and the HD air filter cover which you will need. For less than the cost of the assembly you can get all you need with the following parts
503 81 78 01 Air Horn HD $8.07
503 81 80 04 Air Filter $27.26
537 21 32 04 HD Air Filter Knob and Screw, originally a two piece item now just one piece
503 81 77 01 HD Air Filter Cover $22.34
These prices are from Oct. 2010 so they may have changed. You can buy aftermarket HD air filter if you wish to save a buck or two but you can NOT use your existing 365 low profile air filter. No price for the one piece knob and screw, the two piece setup i bought was $6.15. Wouldnt think it would be terribly different. Not hard to install. Shroud needs removed, unhook choke lever, unbolt existing air horn. Reinstall in reverse, dont over tighten bolts on new air horn.That should do it if my memory serves me correctly. Trim limiters on carb while your there if you like.