A carbed 502 only has alarm sensors for 3 things. Oil Pressure, Water Temp and Drive lube.

The alarm goes off when the circuit is grounded/completed. IE.The drive lube sensor drops to the bottom and completes the circuit.
If disconnecting the sensors does not shut off the alarm, then one of the alarm wires is shorted and grounding out against something.

you have a BAD oil pressure switch and or water temp SWITCH NOT sensor these are 2 different things o r shorts in those circuit(s) - UNPLUG the swtch to see which one as the alarm should go away. Its a simple test

Next is the warning horn itself shorted if its not I said above

OK---YES--the alarm system worked after we put the new engine in------After a few hours she went off and after one by one pulling the sending unit wires off-I found it was a faulty oil pressure sending unit----replaced same and she worked great for another few hours......Alarm rings again and once again I pull each wire off and now all three wires are off-----oil pressure--water temp--and drive fluid bottle and the alarm is still ringing-------I followed all the wires from the sending units (which are all brand new wiring harness) and could not find any bad wires or grounding wires.....I will buy the alarm horn now tomorrow and change it out w/ my fingers crossed---------------
Thanks------Mike--Tampa Bay