hello so cal gl i have 996 c4 calipers on all 4 corners , a similair setup to you i used all the 996 disks but made some 5mm spacers for the back and mounted them on na944 steel arms ,go to ricola,s site he has a very good write up on the conversion , on the front i turned down a beetle front hub as a disk carrier it works very well and is the correct offset for the radial mount bracket , as for mc i use a standard 2 circuit beetle mc ,with the big brakes it took several attempts to get all the air out over a couple of weeks but the pedal is now very hard
and works very well , if you go the porsche mc route this is only required if you want to alter the bias front to back , it is recommended to put the 19 on the front still and 23mm on the back
hope this helps
cheers jon