Extending bucket seat legroom

I have bucket seats and want more legroom. My 72 Duster 340 has a 4 speed and it’s nearly impossible to shift into reverse. My knee is up against the steering wheel and shifter. I’m 6’4” and want to move the seat back 4”. Has anyone made or used anything that works? I have seen aftermarket brackets for Mustangs.
Any help is appreciated.