It's OK to use Ghia disk upfront and 944 rears. The brake pedal might be a little low for you but you can change to a MK1 MC(rabbit) 76 to 83. The mK1 MC has a slightly large bore. I dont have the correct measurements, Ill look for them.
Lanner at
www.vdubengineering.com agreed with this.
PS.
He is "the man" when it comes to 944 conversions. Buy some of his stuff!!!!
Bryan