From the sound of it, you would need to verify that any fluid is getting through the front Steel lines to the hoses. If none is there after applying pressure, then it's a sure thing that the Proportioning valve is stuck and isn't allowing the fluid to the front steel lines. Otherwise, I would make sure those new calipers aren't defective and stuck or clogged. There are some You Tube videos on servicing a valve, not Pinto specific, but possibly some help and very informative. ( Check out the Mercury Cougar one)
Good luck and keep us posted,
Pintosopher