According to the MOTOR Emissions Applications Guide a federal emissions equipped 1976 Chevy 4.1 Liter engine (for GVW 6001 LBS & OVER) needs to be equipped with:
Positive Crankcase Ventilation (PCV), ACL (Preheat Tube - Air filter to heat shield), and Spark control (distributor advance timing control).
See Photo Attached:
Emission Application Chevy 1976
There is no call for AIS, EGR, EVAP, CAT, or O2.
As far as your Chevy Blazer's vacuum diagram, we can only recommend purchasing a factory or aftermarket older engine shop manual.