Didn't use the adj. brackets, just positioned the seat where i wanted it & drilled the holes, I was looking for least weight as possible, I only drilled 4 extra holes, 2 on each side, If memory serves me, i also used a few strips of aluminum flat stock for better leveling, but i've installed these type seats in 3 different Mopars, One of them i used the adj. bracket & wasn't too impressed with it, just need to get creative so you don't butcher up the floor with too many holes.
Sucks you need to move the shifter back, Now you see where my is at, you weigh about like me, I'm 5'9", maybe you'll be ok where its at with the new seats.