Well Purney, I'm with you, I think it is a '57 powerglide 235 and as such would have hydraulic lifters. The head decodes (on the Inliners site) to a '56 but I think these heads were used on later years too. You've got the right engine in your '51 in my opinion. Some of the guys here like the solid lifters but I've got a '54 powerglide motor in my '53 and I like that it's quiet - got more power too.