I may just be stuck with what I have, but...
The original bucket seats in my 73 4/4 are OK, but not great. I did redo the webbing in the bottom half, but they are fairly firm. And the back has no lumbar support to them. I don't want to add a lot to them as I am 6'1" and need all the room I can get. I was thinking of taking the base apart and adding a sheet of some sort of jell padding to make it softer. I've never taken the back apart, and I'm not sure what would be involved in adding some support. Or if there is an additional pad I can just drop behind me. Most lumber support pads I've see are rather thick.
I had a dream the other night about a lumber support with a small air pump attached to customize the support. Does such a thing exist?