This is a special made fitting, the first of it's kind, that attaches to a 1975-79 Ford F150/ F250/ F350 oem evaporator and accepts a #10 standard barrier hose. This solves the most difficult part of getting your oem HVAC working with other modern components. 

ACL3 is a 90 degree fitting. 

The fitting size is #12 male insert o ring which has 1 1/16-14 threads. It accepts a common #12 o ring. It accepts #10 standard barrier hose, which is extremely common. You can do the beadlock crimping with common and affordable tools. 

I highly recommend keeping factory HVAC. It outperforms expensive aftermarket setups.