Your current Unit Load is 60, which is fine (1 Unit Load = 1.9 Watts, or 114 Watts total for this cabinet).
However, swapping all three 008 boards for 024 boards causes several problems:
1. You exceed the total Unit Load max of 96 (by 24 Units)
2. You violate the max board-type count (a total of four 024 modules per carrier in hybrid/PBX mode,
and three 024 modules per carrier in Key mode).
3. You would have to renumber the voicemail ports if you replaced the modules in slot 8 or 9.
Given only what you've posted, I recommend replacing the board in Slot #11 and nothing more. This will increase your station count by 16 and bring the Unit Load total up to 80, which is still very acceptable. And unless you have a third cabinet that we don't know about, you will not have to renumber any stations.
You could actually replace two of the 008 boards and still be barely within the Unit Load max. However, I'd prefer to see your entire inventory before making that or any other suggestions regarding board swaps/relocations.
Note: Even if you're running in Hybrid/PBX mode, the quoted ability to support four 024TDL modules in a single cabinet IS NOT gospel. If you've got a fairly large number of 4424D+ phones(for example) in that cabinet's config, then you really need to consider a more conservative number of 024TDL boards.
