Need more leg room in Elcamino

I gave my dad a '67 Elky with buckets/console. It's a nice ride that he's admired since I got it so I let him have it (I have other rides). Anyway, he is a tall guy and does not have enough leg room to be comfortable. The factory buckets only go back to the metal tray under the back window. I recently saw an elky with earlier (64-65) buckets that are not as tall and fit under the tray thereby allowing the seat to travel further back. Is anyone familiar with what I am talking about? Would I have to move the tracks further back? Any other ideas? I'd appreciate any help.