340 or stroker motor!

I have a real rare 377 cu.in. Motor making 650 H.P. on pump gas. The Block Casting is 3614530. with a round KB in a circle on it. It is a 4 bolt main. Makes 650 H.P. with the Dyno sheet at Koffel's Place. Early Mopar Aluminum Heads. Pump Gas. These blocks are called the Mystery blocks. They were used for the 70' Trans Am season. Supposedly only 20 left. I would let this go for $5,500. I am in Michigan.