The ratmotor didn't come out until 1965, so it isn't a 50's pickup.

If you think about your question for a minute, you're asking for an estimate on an engine that is unidentified, and with no idea if it runs or not. That isn't much of a description to work with.

I suggest that you look at this site, then find some numbers for reference, and the number of miles on the vehicle if possible.
http://www.roadsters.com/bbc/#blocks

On the other hand, if all I knew whas what you posted, I'd hand over $20.00 and hope I wasn't buying a boat anchor.