The Chevy tri-five, refers to the Nomad and Bel Air models 1955-through '57 in particular. This period marks a time of change for Chevrolet, GMC and the whole auto industry in North America. The 265 (4.34 L) small block engine introduced in '55, is the base for the complete line-up of GM small and large block engines for the next 40 years or more. The top model, the Nomad wagon, has a MSRP of $2,608 with the entry level 2-door sedan valued at $2,025 in '56. New options available in '56 include a rain sensing automatic convertible top, padded dash, and seat belts complete with shoulder harnesses. There were no takers in '56 for the rain sensing top and only about 7% of customers opted for the seat belts.