1968 RS Z-28 info needed.

[BigD69]

A good friend of mine passed 11 years ago and his wife contacted me about helping her sell his 1968 Rally Sport Z-28. I looked the car over the best I could in the trailer its stored in, no documentation, color change. Motor is gone, it has a 12 bolt looks to be new replacement 4 leaf rear springs, no factory gauges, 4 speed speedo cable original matching number Muncie, 4 piston power disc brakes, engine mounts are missing, how can I tell if this car is a real Z-28? I have the trim tag info. He did collect as much correct 1968 302 parts he could find, almost a complete correct motor but not original to this car, he did not find a MO block but does have a DZ block which I know is a 69 block. I told her to sell that block separate. What's that bare block worth?