1990 Accord, Replacing ECM

HI, I own a 1990 Honda Accord, LX. I'm just wondering what would be downside, if any, if I change out the ECM from a California to a Federal part number? It seams a lot of the troubleshooting leads to " Replace the ECM with a known good unit..." and I'm having trouble finding a used California ECM to use for this purpose.
Thanks,
Steve