Many confusions above!
Right, a quick summary to make it easy.
Forget ALL and ANY rear calipers. they are all dangerous. 352 in a porsche part number denotes a rear. 351 is a front.
Forget anything that uses a 312mm disc - they're useless and too small.
Forget regular boxster fronts. They will only take a 25mm wide disc, which limits you to 312's, they leave a nasty unswept area, and are generally fairly ****.
If you want porsche brakes, you have 3 options.
Option 1:
996 fronts. These are part numbers 996.351.425 & 996.351.426. 36 and 40mm pistons. the same as LCR brembos. Found on 996 c2 / C4, and also Boxster S fronts. They are radial mount and will mount up with creation motorsport carriers to a 330x28 alfa brera disc which you'll need to redrill to 5x100 PCD.
They will also work on a 323mm LCR disc, but you'll need to machine 3.5mm off the carrier face due to the radial difference. These are probably the best option in terms of performance / weight / running costs. Pads are cheap, as are discs. they are also ideally suited to the 8L master cylinder.
Option 2:
996 Turbo / C4S fronts. 38 and 42mm pistons. These are part numbers 996 351 429 & 996 351 430. These are also radial mount, and carriers are available to mount them using a 334 x 32 R32 disc. Performance wise these are pretty epic, but pads are more expensive, and discs again considerably more so, and they are a fair bit heavier than the above. These are slightly larger hydraulicly than the regular 996 fronts, but not enough to upset pedal travel. Well suited to a mega power monster like Staceys car.
Option 3:
18Z 6 pots. I don't know the part numbers for these, as they're not something I'd ever entertain myself. They're a brilliant caliper, but poorly suited to the 8l 23.8mm master cylinder and will give a long pedal travel. they can be mounted up with R32 discs, or redrilled Mercedes ML 350mm discs with the right carriers. I wouldn't bother though. This opinion will upset others (Sorry Sam xxx)
Stopping wise, LCR brembos with the same pads are just as good as the 996 fronts, but the LCR do use a fairly small and slimline pad to aid wheel clearence. This means they're wheel friendly in fitment terms, but more expensive to run than a 996 front as the pads start off quite thin from new so you get less lifespan from them. Not a huge issue on a road car, but more of an issue when tracking it.
To do it properly, the LCR setup WILL still be the cheapest. the reason the porsche calipers appear so cheap at the moment is because you're looking at all the crap ones. expect to pay ~£400 for a set of 996 fronts worth using.
Hopefully the above is of some help
I thought I'd reply here rather than to your PM, as others may benefit when searching in future
