Why do you want to keep the old one?
If I were you, I'd replace the existing tint, and re-install it. This way it will be new, not faded, and matching. I'd also check with the Texas DMV or DPS and find out what the legal limit is, since Maryland has a 35% limit. You should have something lower than that, like a 20% or maybe even 5% :D
Good luck.