Welcome to the site RPB.
That looks like a good platform to start from. Many folks pull up the flooring to get a good look at the rust situation on their bus.
If your bus lived in Texas all its life, more than likely any rust on the floor is minor.
The engine appears to be a big block 366 cubic inch, vs 350-6.0 like you show in your profile stats, (The 350 is actually 5.7 liters).
One easy way to tell engine type is the number of bolts holding the valve cover's on on each side. If 7, it's big block, if 4 its small block.
Good luck, and post pics of the conversion if you can...