does anyone know what items were cast on the tiger I E. I know that the mantlet , rear deck , and the snorkel cover were. any other items? does anyone have ideas on how to make the casting numbers that were placed on these items by the manufactures?

Welcom to the site. I can assure one of this wise folks will respond to your question shortly.
Great to have you here
DJ

Many other items were cast including the spare track brackets, certain examples of the hatches and exhaust "covers" for lack of a better word.

The latest book on modeling the Tiger I is the AWESOME book from Angus Creighton. He really does a great job and even shows how to make some of the more prominent casting numbers/marks.

Casting numbers and marks did appear on all cast items.. This practice is not unique to "German engineering"... just look at any Sherman or T-34 to see the numbers all over the place.

One obvious choice for casting numbers is the spruess from the kit that you are building. Some of the numbers for the parts are small enough as to be usable directly. There are a number of photoetch sets of numbers, I have seen Aber and Show modeling.
There's also the numbers from Archer Fine Transfers.

Hope that his helps.
Tim