The answer is simple. Just run the original hard Drive LED block to the 2 pins next to the SCSI III port on the CS.
*Note*
LED's have an Anode & a Cathode. Get them the wrong way round & the LED will not light.
If you get it the wrong way round, it shouldn't do any harm.
Spin the block & it should all be "Flash-a-rama" for you! :-)
Not sure if the A3000 uses a 3 wire block for 2 wires like the A4000, so getting the block on could be a sod without a mod! ;-)
If you still want your A3000's SCSI to flash as well, you're going to have to fit another LED to the Miggys front panel.
As zipper said earlier, it's nice to have individual LED's per Drive, then you really know what's going on with your rig.