new gauge cluster now wont start

Its somewhat common for the unknowing to see a black wire on the amp gauge and assume it is a ground. It is not a chassis ground. The current goes right through from red to black and does reach chassis grounds at the ends of the various branch circuits.
A volt gauge should have positive side attached to a dark blue w/white tracer that is hot at switch on. It feeds the instrument panel so you should be able to find and tap it at the panels harness connector. Negative side of the volt gauge does go to chassis ground.