'67 Imperial would have had the 4-piston Budd brakes.. Pretty much the last discbrake system you want to swap to.

If fabbing a brake system together from existing Mopar-parts is no option then you'll have to spend money.
But, personally I would be miffed if I had shelled out well over 13-1500,- Euros (for barely adequate rotors) and I would still have to figure out possible brake-bias problems.