Regulating vacuum

Ok, so.... I’m restoring the dash and heater box on my 70 barracuda and I want to test all the functions of the A/C heater box. FSM says to apply 8 psi of vacuum to the switch to test functionality of the doors and switch.
I’d like to use a A/C vacuum pump to provide a steady source of vacuum as the dash and heater box are in my basement. Is there a way that I can regulate the vacuum so it doesn’t suck the diaphragms out of my 51 year old vacuum actuators?
Hoping someone here has an idea.
Thanks

Do you have a Mytivac?
If not you will need to create a huge bleed for your pump
using a adjustable needle valve or similar

You can actually use a Grainger valve for this.