Can the injectors on an LT1 be immersed in carb cleaner or an ultrasonic cleaner?

 

no, it can't.
symple

 

They're cleaned by putting them in a fixture that runs cleaning fluid through them under pressure while pulsing them on and off much like your car does while running. Then they are usually che cked for rated flow. Some of the places that sell injectors offer this service. Also, you can run good gas and various cleaners like Techron to keep them clean, but if you're talking aobut 13 year old injectors that need service, it might be hard to clean them up that way - it's more for maintenance.