What other clues is their for not being a z28 that you guys can see

 

11/16" rear sway bar. I don't think that proves it is a Z because I think it came on the F41 option but no rear sway bar would indicate it was not a Z28. Front sway bar should be 1" not 15/16, that is one I will bet gets missed a lot while building a clone.

Both the rear and the trans should have the partial vin number. So the numbers could match the last 5 digits on the dash.. It does not matter much with the original engine gone most of the value of it being a "real" Z went with it.

Just a FYI for every real Z28 there are at least 5 fakes out there. If you can not trace it all the way back to the original owner with documents you should just assume it is a cone because you can never prove it to anyone else that it is not. You would be amazed at the length guys go to prove there clones are not clones. You can even order all the original documentation properly aged. the last build sheet I saw even had a coffee stain on it to make it look real.