PLEASE help, CO2 tank question

Hey,
I have a question that I have not been able to find an answer to & really don't want to ask a gas supplier a shady question like this, please help! I have numerous N2O tanks (15, 20, & 50 lb.) and am wondering if I could use them for CO2 instead for my new, & 1st, grow. Anyone know if the psi and valve are the same? I believe the psi is, could be wrong to, but have no idea if a regulator will fit on the N2O valve. Any idea if they are the same? I really want to rage the CO2, but can not afford to buy a new tank right now. I've looked and looked for answers & have found none... Can some one please help me with this? Any info would be greatly appreciated. Thank you......

Okay, a very helpful individual helped answer this question somewhere else & to any one wondering I was informed that the n2o tanks will hold co2 just fine. I am still slightly unsure if the actual tank valves are the same, & if a regulator will fit the n2o tank valve so if any one knows, please reply. Otherwise, I will post my findings once I figure it out. I am going to try to get my 15 or 20# tank filled within the next few weeks and once I do, I will attempt to fit the regulator on & we'll see what's up...
P&L

the tank will work. the valve is a cga 580. co2 is a cga 320. some gas palces will or can have the valve changed

n2o is nitrous oxide. forget the cga for it 326 I think.

co2 can go into any tank rated 1800 psi or higher.

you can ask me anything about compressed gas cylinders. I did cylinder maint. for 7 years and was the plant manager of 2 years. If I don't know it i can find it.