for my CJ, and soon for my 715, I have built a locking bar that ties the brake and clutch pedals together, and also covers the accelerator pedal. Locks with a padlock, which is protected from bolt cutters. I will try and remember to get some pics.
No key switch, but three separate switches, 1 hidden, 1 disguised, must be on in order to power the HEI.
When I finally get it on the road, it will live in the garage, so only problem is in parking lots when I'm gone to town.
Ditto the above about trying to lock the doors with a ragtop, they'd just cut the rag top here.