My mother can barely see over the instrument cluster shroud. At the same time, she has at least a foot of headroom, and her legs are not really being supported by the (non-adjustable) drivers seat. Are there any aftermarket seat rails or adapters which will raise the seat 2-3"? This should still work for someone over 6'-0", as I have at least 6" of headroom, and the steering wheel can be tilted up out of your lap.

 

You could try a wedge cushion seat such as this one:

Amazon.com: Driver's Seat Lift Cushion: Automotive: Reviews, Prices & more

or this one:

Amazon.com: Wagan IN9788 Ortho Wedge Cushion: Automotive

or this one:

Amazon.com: DRIVER'S ANGLE LIFT SEAT CUSHION WITH WASHABLE SEAT CUSHION COVER: Electronics

Tempurpedic has some really nice ones if you don't mind spending more:

Lumbar Support Seat Cushions from Tempur-Pedic -Office, Car, & At-Home Back Support