I got a aftermarket temp gauge and the connector on the engine is not the same as stock, I heard you have to drill a hole, but is there another way?

 

There should be several plugs in the manifold, heads or block that go into the water jacket, with a pipe thread adaptor you should be able to adapt something. I think you can get a aftermarket tharmostat housing that might work also.

 

X 2 on that.