I'd make sure the adjusting rails are workin right, and you've got the seat all the way back - also make sure the arms that the seat back pivots on are the right shape and don't allow the seat back to "recline" too much - then make sure your pedals are properly set to have the original travel [they can come up too high if the stop bumpers are missing] - then try doin lots of situps for a few months so that stomach flab can operate your legs properly LOL
you could also change the stock 59 wheel for a 55-6 wheel, that doesn't stick out so far so that it's easier to sit up straighter - I too am 6' something [lessthanwhenyounger], and don't find it cramped in a TF, tho' some of us do have longer legs than others - last resort you could try a seat from 1988 up GM truck, which are nicer seats and fit well [don't hafta move out the tank, which prolly won't really gain a lot of room seatwise anyway
Bill