Many of the MIL-SPEC gauges were put together pretty tightly - very good near hermetic seals that can be diffficult to get open.

Look at them closely and see if there is an entry point (screws, etc.) Even so the glass may be hard to get out and you will need to get new glass made.

That dual scale (kM/miles) speedometer is unique - I've never seen another. Is the temp gauge in degrees F or degrees C?