I'm 6'2'' or 3 and I could use some extra leg room in many small (and some medium) cars. In sports cars, head room adds up to the possible issues (the mx5 being the worst, I'm eager to see the new one). On the MR2, I did some mods to fit with my racing helmet
IMO, the issue isn't that much about having the knees hitting the dash or wheel (I'm skinny and wheels can tilt) but it's simply that having the tighs not supported properly by the seat cushion isn't comfortable and gives cramps. In some cars, if the problem isn't that bad, a good option would be to put some big washer under the front mountings points of the seat, giving more tigh support without eating the rear seats legroom or doing serious mods (cutting, welding).
Usually german cars offer more generous room, even the Mini has plenty of room for the driver. I don't know why japanese and most US car makers persist to make short rails, it costs about 1,50$ to get an extra few inches of steel.
Otherwise, 250$ for a bracket kit seems like a racket. And in some cars like the 2012+ yaris, they improved the legroom compared to the 06-11 but since the steering is non telescopic and not specially close to the driver, going more rearward would just cause issues with the steering wheel being hard to reach comfortably. In many cars it will also make the door side armrest inefficient.
I like motorcycles for that, zero adjustments and the ergonomy is usually fine.