According to a book I have, Chevy pick-ups 1946-1972 by John Gunnel, 1963 intoduced 2 new sixes. The standard motor was a 230 and the optional motor was a 292. The 230 is described as an overhead valve design with wedge shaped combustion chambers. 140hp/220torque. The 292 had aluminized inlet valves and chrome top piston rings. 165hp/280torque. This is what they would be if your motor is original. Hopes that helps narrow it down.
