[Dave at Pelican Parts]

The adaptors are only for the driver's side, and the 72+ passenger's side. With a 70 or 71, you're stuck. Unless you want to weld in the bits on the floorpan that the seat brackets bolt up to.

Hard-mounting the seat is one option. Don't cut out the cross-member unless you have other reinforcement in place. Figure out some way around it. You'll need to do something about the backpad as well; I assume the later style one just bolts in... But that should give you more room to fit the seat behind the cross-member.

--DD