I want to place a set of mechanical mini gauges in my 66 Cutlass 330 cube without losing the use of the idiot lights, any suggestions on how to modify or replace the senders?

 

You can tee the oil hole to two, may need to put a sender in a radiator hose for the temp.

 

I'm not familiar with putting the sender into the radiator hose, would you please elaborate?

 

Something like this hose adapter:
https://www.summitracing.com/parts/flx-32082/overview/

 

Thanks, now it makes sense and a solution to my problem.

 

To expand on the answer a little, pressure senders like oil pressure can be mounted on a tee. They only need to see pressure, not flow. A temp sensor, however, needs to be in the flow of coolant. If your intake does not have a second port in the crossover at the front that you can use, then the radiator hose adapter tube is your only option.

 

I thought I'd be able to purchase a thermostat housing with an additional plug to use but between the top radiator hose and a water pump bypass there isn't any room. The engine only has one spot and that's already taken up by the idiot light sensor. Splicing the adapter into the hose will work out good as I'm planning to flush the engine and replaces the hoses and thermostat soon. The oil pressure looks easy enough, next will be where to tap into the panel lights.

 

You can get those for Chevy motors, not for an Olds.