I agree safety was a concern, but I did do a few additional mods you can't really see to help this.
I put late model shoulder seat belts in it, Granada front discs, it was already a factory PS car so I converted it with a late model pump, and I put a Mustang Steve's power brake set up on it. It uses an Escort booster - about $75 rebuilt - and Steve's $20 plate for the pedal hanger to make it all work - works fantastic - really stops like a modern car.
I completely rebuilt the chassis - so it handles OK. I'll put more modern stuff on it one day, but for right now it runs and drives really well.
I also put a full steel plate between the trunk and passenger compartment - bolted it in and sealed it with fire proof race car seam sealer - just in case of a rear end collision.
The car was originally a factory 4 speed, but my wife forbid me from putting in a late model 5 speed - so I got a donor GT drive train with an AOD.
This is about as safe as you can make 'um.
I've got about $7000 invested total - and could easily recoupe my money - and I think it is safer than any modern econobox for the money - except for maybe an airbag. Plus we had a ton of fun building it together - you can't beat time like that with your kids - AND she will be a Mustang lover forever!