Starter and switch Issues, Need some help

I am building a 74 duster and I installed autometer gauges into dash, I have the voltmeter, fuel gauge, and tach wired into big black wire on steering column. When I start the car, the starter stays engauged. I could turn switch off and remove key, and it may stop or it may keep spinning. I am confused about this one, Is my switch going bad or have I done an Oopps in wiring.