[StreetSnake]

I was hoping the vast knowledge on this forum could once again help me out. I recently picked up a 67 Terlingua Mustang which has 2 650s(I found out) atop a 302. In the process of deciphering what cfm carbs I had I noticed the intake looks to be an original FoMoCo high rise 2x4 manifold. My question is; Are these exceptionally rare? I was debating going to a single carb setup and if I could sell the original to recoup some money it might sway my decsion. I hope you can help or at least point me in the right direction. Any estimates on value would be great too. Thanks again