How much more space do i have left for my 40 gallon?

Go for it,should be fine. Don't add them all at once. I'm uming that your tank is properly cycled and has been running for several weeks ( at least 6 weeks). If that is true then begin by adding 4 or 5 fish and then allow the bacteria that run your cycle to adjust for 2 weeks ,then add 4 or 5 more. Don't rush the system and everything should be OK.