[44SAA]

I just completed a heater core swap on the ol 1980 and it can blow some serious hot air. Time to work on the defunct AC system. PO said AC has a leak(s). When I bought the truck the PO gave me about 20lbs of R12- thus I have zero interest in R134 conversion. Truck blows hard but only ambient temp.
Questions:
Is it possible to perform a leak check without charging w R12 first?
Can shops still leak check for a R12 system?

Thank you