That's one hell of an easy retrofit. But I wouldn't use autohold. Mine came with it and I used it probably three whole times. Eventually the parking brake actuator failed from normal use (of course it would, the lever and cable were flawless for a 100 years) and it's an expensive part. No way would I put the additional wear on it using that feature.

I did get the actuator rebuilt and it arrived home today. I'll report back in my original thread once I've reinstalled.