Thanks for all the replies but this was about who had done it and how, not why or why not to do it, or if it was necessary by law. But since it's gone that way, here's my .2...
The purpose for the seatbelts in my case is because:
1) keep my daughter on her butt. hard to stop a 5 year old's impulses!
2) how can I tell her she has to buckle up in our normal cars if I don't make her do the same in this one?
3) so she doesn't fly through the windshield if we need to stop suddenly
4) so she doesn't distract the driver by suddenly jumping in their lap for a hug
5) roll overs and large crashes are not the only way to get hurt in a vehicle. My cousin was sitting at a red light when another vehicle that was crossing spun out and hit the side of her car. This was not a big enough impact to crush crumple zones or set off airbags yet she was sent into the passenger seat from the impact! And that is with a seat belt on! I do not want my daughter being thrown out of the vehicle possibly into oncoming traffic in a case like this! We won't be driving on deserted roads in the middle of nowhere. We live in a suburban area that requires crossing multiple busy intersections just to get a few blocks away. So being thrown from a vehicle in that situation is never a good idea.
I understand not putting them in if you are doing a full restoration. That is not our goal and we would like to be able to run down to the store on the corner in it.
Now back to the topic at hand.... how did you install them, and please post pics.