Adaptor plates could be made to offset the seat backwards. The original track studs would have to be shortened. The adaptors would need to be a minimum of 3/8" thick and probably 1/2". This would raise the seat some, but it may not hurts as the seat is moved back.
Use 1/2" x 1-1/2" bar stock. Dill and counterbore for 5/16" bolt (fron the top side), then weld the bolt heads in the counterbore. These welded bolts replace your original track studs and must be at the same center to center as the originals. Now, move back on the bars as far as you want to move the seats and drill and counter bore the other side of the bar stock for the 5/16 studs that are on the tracks. Mount the adaptors to the tracks with nuts and cut the original studs flush with the adaptor, then set the seat with the mounted adaptors in the car like you normally would.
Keep in mind that you would need to leave plenty of adaptor length towards the rear to allow for your intended offset and if the seat ends up overhanging the box, I would suggest adding some support down to the floorpan.
I have not done this, but I have recently became very familiar with my seats and can see this working very well. Some thought and inspection should be given to the height that adding the adaptor creates.
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