Indentification of frame year needed

[RustMaster87]

I recently picked up an 84 Silverado 4x4 this past weekend. I have spent the past few days going through it and need some help with the cab mounts. The previous owner installed about a 4-5 inch body lift and built it out of whatever he had lying around the garage. From what I can see, it looks like it is an 84 cab on a 73-80 frame. The front frame horns have been butchered to fit the 81-87 bumper. Is it possible to tell by the actual mount on the frame? It looks like the previous owner used both 81-87 and 73-80 components for the bushings. I am trying to order the correct mounts but I just want to make sure I order the correct style. The previous owner was a hack and I would not be surprised if the mounts on there aren't the correct ones.