I have a 52x40 pole barn but because of the way I designed it I have a main room that is 32x40.
In that room you can easily put 6 cars with no lift or work benches: 2 rows deep to 40' of 3 rows across simply pulled and parked. If you want to start stacking you could prob get 5 in sideway along one wall and then 2 pulled in straight down the other for a total of 7 crammed in...I have had 5 cars in the garage...2 shells pushed in close to the wall, 2 cars parked, and one car being worked on. Even with a lift you could still fit 6 cars in roughly the same configuration.
However, I said this is without work benches...so if 30x40 is your total working area I would say are looking at 4 (5 if you count putting on the lift and putting it in the air and parking one under it) with workbenches along the 40 foot wall on one side.
2 shells 'stacked' close to the wall
Room for a full size truck plus more in front....(right now I have a boat sitting in this location)
If you look close you will see that I also have 2 other mustangs in the picture.
I'll post up a bunch of pics off various fill levels of cars and stuff in the 32x40 section of my pole barn
The window you see in this photo by the white mustang is at teh 32 foot wide mark...as you can see though I have a 'side room' that is 20x20 that I open up into
The tall poles are the 32 foot mark from the far wall in this one