Is there anything special to look out for when inspecting a 1970 Dart Swinger?

what rear end it have 71/4? THAT HAS TO GO , BRAKES trunk frame rails crossmember all need to be looked at closely , new dash how was the wiring done , kickdown not adjusted properly can melt a transmission . Pass and keep the El Camino at least you know the history of that car
Also did not see a wiring box on the firewall , not heater core or controls to much wrong with this car and that is only what we can see , imagine the crap we can't see