Removed coolant overflow tank now airbag light on

Here's some helpful diagnostic info:

Mustang 1995 Air Bag Diagnostic Codes

If you look at the codes, you'll see one for Circuit Open, Bad Ground and Intermittent or Repaired. Bad ground means the sensor is not bolted down right; Intermittent means the problem has been fixed. Circuit open in your case sounds like a cut wire or the wires are pulling out of the connector. It can also be corrosion on the spades in the connector itself. Try a bit of electrical contact cleaner on both ends of the crash sensor plug, and see if the error changes.

Nothing in the bracket itself is linked into the airbag system. Did you lengthen the wires leading to the CCRM (the black box on the overflow tank bracket? Is it bolted to the frame again? It is grounded through the bolts that held it to the bracket.