'69 Valiant 4-door w/bench seats - cramped at 5' 10"?

you might try bucket seats ...they are easier to move forward or back by the location you drill. Plus buckets sit lower than a bench.

I proved that with my 68 dart because I went from bench to buckets and its noticeably lower.

I have the opposite problem as you because I am 4'9" and a small person so I have had to do pedal extensions and stay with a bench which sits up a little higher and gives more view over the dash for shorter peeps.

Only problem is that 68/9 bucket seats in nice condition are worth a nice penny