Jeff,
The replacement for the W series is the new Aerolite line. This is a direct fit, same pad, same-same everything but now with the fixed bridge. The calipers can be had in black, red and in a nickel finish. All are fit with anti knock back springs and all can be fit with thermlock pistons if this is a more hardcore track build. The nickel is more suited to that also as it does not trap heat.
http://www.wilwood.com/Calipers/Cali...o=120-13294-BK
If you would like to consider that options shoot me an email with the choice and remind me of the zip code please. I'll see what the xl sheet has to offer you.
toddandchris1@cox.net
Todd