why didnt you ask these questions before you bought the disks ???

________________________________________

Team allesclar ®

Unless you are upgrading to better calipers you do not need to worry- a 6 set of calipers and pads would be the obvious step up for the 266mm xsi type. Make sure yours are in good nick and buy decent pads-drilled and grooved are prettier but not a great move unless they are high quality as they can be a backwards step if they are cheap ones.
Your questions
1 No special calipers needed
2 Car specific as the fitment including offset are at least model specific (306)
3. No, Ford ones may be entirely unsuitable
4 Pads are made to fit calipers- they do or don't fit. Some calipers-brembo for example may have different pad fitments for different car fitments. Manufacturers calipers made for a particular model fit a particular pad-although different friction compounds may be available.

________________________________________

New Forum same high quality intellectual debate!
Team Zimmer™

6 calipers need 283mm discs, and with scrappy items unless you can try them fitted you are going to have to look very carefully for signs of corrosion/scoring on the pistons and for signs of leakage. Since your entire future and that of everyone else on the road is at stake if you can't be sure look for some from a trustworthy source.
If you find some get them at least looked over by a good mechanic.

________________________________________

New Forum same high quality intellectual debate!
Team Zimmer™