The residential tower where Tower 8 is now was changed to the Regent. The new office tower that was slated to replace the First Security Building was shifted to where Tower 8 is now after that building was saved.
This can be seen by the below withwith Tower 8 as blank and a shorter apartment building along 1st South at 2nd East.
When the office market began to boom (prior to 111) CCR released their initial design and concept for Tower 8 as a 22 or 23 story office tower. This design got scrapped shortly after CCR took over the construction of 111 as a way to make it fit in better with the City and less reminiscent of the old Key Bank building prior to the construction of CCC.
The taller glass tower (estimated to be 450') was originally slated to replace the Deseret News Building along 1st South across from the Regent. It was a place holder only as design and usage wasn't finalized. It's only appearance was in the wooden mock-up of City Creek and was on display in the 99 West sales center. I think it was removed at the same time that 111 construction began.
If I have time, I will go through all of my images and documents to see if I can find images for both of these.