I have shops with 10' and 12' doors. You may be able to squeeze more out of it but generally your door height is two foot less than your sidewall height to allow room for the door tracks, etc. So with your 10' sidewall you would have 8' doors and 12' sidewall 10' doors.
I have a lot of equipment and vehicles. I have a 95 hp tractor with a cab, an International 33,000 lb 4x4 truck, enclosed trailers with AC's on top, and all of it will fit (barely) in a 10' tall door. RV's or semis might need something taller but most stuff you will encounter will fir in a ten foot door. That being said there is no way 8' would cut it.
