[396ci]

I had one for sale similar to yours with the 3 holes on each side of the floor mount. A guy at the swap meet said that it came out of a van and not a blazer (never could confirm). But mine did have the long vertical slot for the tire bolt instead of the two separate holes like yours. I would say they are still forth about $400-$600 depending on how bad someone wants it. (pic from internet for reference on bolt slot)