How rare is this?

[richardv6]

Proto type block? On center stage block (4x151981) how many made and whats your opinion on worth.

 

[750H.P.V6]

Unusual but not rare to be honest. I've had several of them, other than the casting # it's a very early On Center block as you said. What's nice about these is the wet sump oil pickup provision. As far as it's value, I'm not honestly sure $4k as a guess.

Neal

 

[750H.P.V6]

Here are a couple of pics of one I had a couple of years ago.

 

[750H.P.V6]

Your block appears to be a bit earlier as it has stepped main registers for the #2 and #3 main caps as well as a production style #4 main cap.

Neal