With the LS1 you won't be able to get a check engine light out of the ECU as it's a signal processed by the BCM. You could use the
oil warning light but would have to plumb in an
oil pressure switch.
I'm running the same lights and have all the others apart from
oil and engine. I've found a neat little circuit to do the seat belt warning light. The whole thing fits inside the bezzel.
I've also converted all the lights including the instrument lights to LED. I hate changing dash bulbs as it's a pain to get into the back of the dash. The LED's will probably outlast the car.
Cheers