I went with the one wire lock-up switch. I just tapped into a keyed 12v source, ran the wire to a 2 position switch (on=off) and to a single tab on the transmission. Inside the transmission, a ground is provided when the transmission is in 4th gear only.
I've seen the other systems that use vacuum switches and tap into the brake light circuit, but I didn't want all that stuff either.
Thanks again for all the info you provided. It was a great help!
John