Engine casting number
 

After searching the boards for this info- I did not come up with a good solid answer, so here is my question:
My car is a 1970 911T. Original case was damaged back in the 70's and was replaced. There is no engine serial number on the case AND no engine type number. The only thing on the case are casting numbers:

901.101.102.2R (one side)
901.101.101.3R (the other half)

The engine has the original 2.2L fan shroud, zenith carbs, etc. Transmission is original. I am trying to find out what year the case is from- ie, is this a 1970/71 911 2.2L case? Anyone know a good reference for case casting numbers- I have about every Porsche reference book available and they all reference engine serial numbers and type numbers, but really don't discuss the breakdown of the case numbers. Any help is appreciated!! Thank you in advance!!

Sincerely,
Keith
1970 911T
1982 930

.....Anyone?.... Thanks in advance!

Problem is that castings numbers didn't changed by years, just when Porsche made a significant enough design change that they felt a new number was required. So a casting number could change half way thru a year, or be carried over through models.

Thanks for the information Robert. Your answer makes a lot of sense and explains why none of the references deal with casting numbers very much (except for the 7R mag cases).
Theoretically it should be possible to find what year range my case is from, although it probably does not matter too much. Thanks agin-

Sincerely,
Keith