1968 Chevrolet Pickup Truck Stepside

1968 Chevrolet Stepside Pickup. The truck belonged to my father, o I'll tell you what I know. The big block engine starts and runs, ransmission shifts good, lutch works, rakes work, here is some rust in rocker panels and body parts. I haven't seen many trucks like this one. Not sure on engine size?? Let me know if you have any questions. Thanks