'74 140 door cards should fit early 240s.
The rear seat should fit without hassles. Not sure about the front seats - you may have to swap the seat rails. 140 seats of that era bolt in via 2 bolts at the rear, and a single bolt at the front with an eye to adjust the seat's height.
The 144 Grand Luxe seats look very similar to 164E seats.
VP Auto keeps NOS and replacement leather seat trims, but they're not cheap.