Me Gots Meez some Ford 9" questions!

[prostreetC-10]

Just picked up a 74 Camaro that I am going to turn into a bracket car. Also just found this morning a guy that has a 70 Bronco 9" for sale. Unless someone has changed it out, should be 28 splines and either small or big bearing'd. I don't know if it has a posi but don't care because I'm running a spool. The housing itself is a little too narrow and I don't want to tub the car or relocate the springs. This is just a "for fun" car and don't want to get too carried away. Why I'm interested is that it has the 4.11 gears in it already and that's the ratio I want.

Question is with respects to the third member only, is the only thing that makes it a 28 or 31 spline is just the side gears? In other words, could a guy at a 28 spline 3rd member, remove the side gears for a 31 mini spool and get 31 spline axles to slide through the carrier itself? I will be getting a different housing and will buy aftermarket 31 axles. Just want to know if I can use the 3rd member only. Thanks!