1955 GMC PM150 Engine: 5.3L V8;. 1956 GMC PM150 Engine: 5.3L V8;. 1957 GMC PM150 Engine: 6.1L V8; with Hydraulic Brake System;. 1958 GMC PM150 Engine: 6.1L V8; with Hydraulic Brake System;. 1959 GMC PM150 Engine: 6.1L V8; with Hydraulic Brake System;.