I'm 5' tall and hubby is 6'2" and can if nudged drive Agatha. As Agatha is my vehicle, I drive her all the time and our mechanic (Dave Porter @ Taos Garage Annex) made the seat move a little more forward than norm. He also (I think) put extensions on the brake and clutch. Having done this, the accelerator was still a problem for me. So hubby came through.
He made a pattern from the accelerator pedal and then took a piece of wood, which he grooved underneath and at the top and literally 'hung' it on the accelerator. He secured it by using velcro. This piece of wood raised the accelerator about 1" which was enough for me to use the accelerator with ease.
It is difficult to explain this but I hope I have helped. If you really have an interest, ask me any questions you may have and I will answer or get hubby to respond.
I think that if you don't want permanent extensions, this might work well for all the pedals and when you drive the Healey, you will not have to make any adjustments other than taking off the wood 'extensions'.
Please, please don't get a taller wife. I suspect your spouse would have problems with this and you might not have your Healey. (grins/giggles)