I have two 7's a 87 Turbo and a 91 n/a . Both have after market radiators 3 inch solid aluminum and I can't seem to keep coolant in them car gets hot it comes out of the radiator caps!
What have others done what pressure caps to use?
What thermostats to use? I need help bad!

 

Mazda thermostat only. You mentioned that there's a 3" aluminum radiator, but if you still have the original belt-driven fan, you have to have the shroud for it as well. Most people can't get the shroud back on after installing the thicker radiator. Make sure the problem is not the radiator cap (pressure tester can be borrowed from most parts stores). I think mine is a 16psi radiator cap. Not sure what stock is, but I'm not experiencing any cooling issues.

 

the shroud is a good thing to have.
Also the plastic undertray.That helps too.
The OEM thermostat is highly recommended in any FC setup(TII or N/A).
Are you running the stock fan or an electric fan?
can you post pics of what your engine bays look like?

 

No shroud e fan yes I will upload pics just installed 11 lb cap. I unplugged my e fan and the small one up front still running seems to stay cool o will take for a drive now and update