Does anyone read the OP's question?
"Any suggestions that would give a good trigger for steel challenge?"
No one who actually shoots steel challenge would recommend a two stage trigger.
You do want a trigger group with a short reset and an original or heavier hammer fall for reliability.
I do shoot Steel Challenge and Rimfire Challenge etc with my 15-22's.
I run a Geissele SD-3G trigger with (longer) 901 Colt hammer/trigger pins.
Super Dynamic 3 Gun (SD-3G) Trigger
Trigger & Hammer Pins For COLT 901