GT Coupe brake upgrade options?

[Ben Swann]

'83 GT Coupe - late build  I'm installing an MC engine in will need better brakes.  Owner wants to keep the 4X100 hubs. 

 I obtained stub axles from both '88 Model 80 which take Girling caliper #36.

Also have a set of stubs from '87 Scirocco(I think) that take Girling #38.

Is there as particular set of rear rotors/bearings that I can buy new that fit either of these combinations in the rear.

Can I use G60s from 5000 TQ in the front without changing wheels.  If so will I need different disks and from which car.

Any ideas or suggestions - keep it inexpensive please.

Thanks,

Ben