If you want one for the 480 then your need 1 (maybe 2 depending on year) and fit it into the rear brake line.
1 X or maybe 2 X RPV1
2psi- 1/8NPTF tappings
£27.35 (Excluding VAT at 17.5%)
2 X FMB2511
2 X TN1-3L
2 X 3/8 UNF end cap unions (from your local motor place)
There are some good comments on the spitfire forum and I'm using a 10psi valve but 480's need a 2psi.
More at http://www.wilwood.com/Products/006-Mas ... /index.asp , Up to you if it's a good idea for a 480 but on drums I can see it being helpful and already in use on some. Thought you might like to know.
cheers
PS:- The prices are higher on the website then I paid when standing in the shop. I got all the above + some unions for £21.