My mower starts just fine, but whenn I engage the deck, or release the clutch it dies. Is there a safety of some sort that I am unaware of? Oil level good, flat ground, sitting on seat.

Sears tractors normally have at least 3 safety switches, all designed to stop you from doing something considered dangerous. The most commonly failed switch causing your type of issue would be the one under your seat. If that switch fails the machine thinks nobody is seated so it will not allow blades to engage or drive to move forward.