That's a good size, depends on what your using it for, probably part storage part repair. Put as much shelving as you can afford and fit in the areas you don't need to bring equipment into, get as much stuff off the floor as you can, I'm a shelf nut but it makes things easy to organize.
And in the area used for repair as many work benches you can fit, you always need free bench top space to have a couple things going on at once.
Since you mentioned pouring the floor this week.
If your driving heavy stuff in there I would recommend 5" thick slab with reinforcing wire. Some might think that's overkill but IMO 4" is borderline for medium to heavy equipment traffic.
Do you have any pictures? I'd like to build something around that size in my yard, My workshop now use to be a house so no overhead doors, I built a 20x40 carport to keep the truck under and another 16x16 shed for the tractor and small equipment, all attached, but would like to have a building again.
Good Luck, JB.
