grinding/scraping noise when I let off the gas

[alden]

I know I've got another thread going about another issue right now but it seems if I post additional questions in previous threads then usually get missed so hopefully no one is offended by my second thread this weekend. I've only taken the truck (1959 Fleetside, stock 235, 4 speed) up and down my street so far just trying to figure out all the little things needed to get it truly roadworthy and the latest is a pretty bad series of noises coming below the cab when I let off the gas.

When I first took off today it made a bit of a clanging/grinding noise but that went away once I got up to speed (as in 20-25 mph), then when I let off the gas there was a pretty loud grinding/whirring noise until I got down to a near stop. I was thinking this sounded like a universal joint issue but I'm really quite ignorant on all of this so I could be just talking out of my bum. Any thoughts on this?

Thanks!
Alden