1979 GMC P2500 Engine: 5.7L V8; Water Pump to Block; Composite;. 1980 GMC P2500 Engine: 5.7L V8; Water Pump to Block; Composite;. 1981 GMC P2500 Engine: 5.7L V8; Water Pump to Block; Composite;. 1982 GMC P2500 Engine: 5.7L V8; Water Pump to Block; Composite;.