Batboard

I have researched as much as I can and cannot find out what RF board I have. I have a HLD4322D. I have seen:
HLD4322B that is 146-174 MHz
HLD4322C that is 144-174 MHz
I have not seen anything related to HLD 4322A or HLD 4322D.
I am trying to get the RX sensitivity the best I can for 144mhz with this radio and some others with different board numbers.
Can anyone help please?

Thank you in advance

They are the same boards. Motorola changes the suffix of the model numbers when there are major changes to that unit. This might be due to component changes, feature or option additions or even major rewrites of system firmware. In this particular case, the changes between the "B" and "C" version allowed a lower freq range. The "D" version would also have this change, the "A" would not. The "A" version would be the original design.