Last two numbers on '79 i-beams

[sofla1966]

I have read that 1979 D8TA-8-CA 46 and the D8TA-9-CA 42 i-beams are direct fit for the front disk swap.
I have found a entire front end but they are D8TA-8-CA 12 and D8TA-9-CA 10, what do the last two numbers refer to? Does it matter?

Thanks in advance

[bruceandersson]

I have installed two 70's I beams for disk brakes in slicks. Simple bolt in with issues. I think mine were from a 77 and a 76. I never paid attention to the actual part numbers.