Micheal,
Willwood do two calipers - the Dynalite II, and the Billet Dynalite. The first is slightly cheaper and the second is stronger.
The Dynalite II is prone to flexing under heavy breaking - some drivers say that gives it 'feel'. But the Billet does this too (but less).
Last time I looked the Dynalite was about &163;90 per caliper and the Billet about &194;&163;120. But you will need a fitting kit to go with
it - and the whole set for this usually costs in the order of &163;500 - &194;&163;600 if you shop around.
Princess four pots will also need a fitting kit for the GT6 upright but in all honesty you will be VERY VERY lucky to find a set you can use. I tried
for over a year to find a decent set and instead opted for a set of GT6 (spaced) for the Capri vented disk. Also, the princess calipers are a real
bugger to bleed - dynalites not so.
Try 'googling' Dynalite II and see what you can find.
NiG
http://www.niginthecar.net