To run the Early Bronco springs, you're gonna have to change out the coil buckets and find a way to caputure the spring at the bottom. You're also gonna have to find a way to mount your shocks to the frame as well. It's a bit of a job but can be done.
TTB coils are pretty stiff so changing them out for a longer length will gain you little if anything but if you are wanting to ditch the coil spacers, that's the way to go.
Some guys have used jeep (xj) coils in place of TTB coils with success but you may have to run dual shocks to control the front end since they are a much softer spring rate...again it's gonna be a job to make these fit since neither the jeep or bronco coils will bolt directly in place of your existing coils.