There are many webpages that illustrate how to put front disc brakes on the '65.  Try Wabba.net for starters.

I swapped front disc brakes onto my '65 using the following parts:

• Master Cylinder - '79 Granada manual brakes
• Stock Prop valve - '79 Granada
• Adjustable Prop valve - From Summit, inline with the rear drums
• Master Cylinder Pushrod - stock '65
• Disc brake assembly from '70 Mustang (spindles, calipers, discs, etc.)

I am currently considering the power booster and MC from a Geo Metro.  This setup has been done on a Falcon, but I'm not sure if it will fit the Stang.