A method of forming a space frame for a cab, including forming each of a pair of hydroformed, longitudinally extending inner side rails, a hydroformed connecting member, a hydroformed first upper cross member, each of a pair of hydroformed upper longitudinal members, and each of a pair of hydroformed A-pillar members. The method including, providing a tubular metallic blank having a tubular metallic wall. The method also including placing the tubular metallic blank into a die cavity of a die assembly, the die cavity having die surfaces, and providing a high pressure fluid into an interior of the blank to expand the metallic wall of the central portion of the blank outwardly into conformity with the surfaces of the die cavity to define the respective hydroformed member. The method further including mounting the connecting member to each of the inner side rails, and mounting the first upper cross member to said connecting member; mounting each of the upper longitudinal members to the first upper cross member; and mounting each of the A-pillar members to one of the upper longitudinal members.