Peter, he has the OEM HID wiring...this is not compatiable with aftermarket HID equipment. The aftermarket HID kits are additional wiring (for power) and grab the signal from the OEM headlight connector to tell the ballast when to fire. He would need to replace the gifted headlight set with an OEM HID headlight for everything to work. I imagine there is different wiring.
EDIT: Peter beat me to it.
I think Peter was stating that why go backward in performance(Factory HID to factory halogen). He wasn’t referring to aftermarket HID.
As you state, I believe the OP was going for an inexpensive(i.e. free headlights) vs. purchasing a new/used factory HID headlight assembly.
For REEDS98GT, make sure you aren’t trying to power the halogen bulbs through the factory HID ballasts. I think you have to go from the main headlight harness(bypassing the factory HID ballast) directly to the bulb. In fact, I’m not sure of the exact details, but you may have blown the halogen bulbs if the HID ballasts tried to “ignite” the bulb.
Double Edit: To Peter's point, are the factory ballasts hardwired into the main harness, or is there a plug(similar to an aftermarket HID kit) that plugs into the factory ballast that can simply be disconnected and plugged directly into the halogen bulb?