|The simple answer is the frame rails....
Front location is the furtherst extension of the frame rails forward very close to where the front 'K' member bolts into the chassis. Rear is the furthest rearward point right where the lower trailing arms connect to the chassis.
If your car has a significant amount of floor-board rust that has weakened the frame-rails, you don't want to go this route as you'll buckle the frame as I did many years ago. Ditto for supporting the chassis by the sills....
Most people tend to support the car with jack-stands below the front 'K' member and under the rear lower trailing arms approximately where the spring perches are located. This method tends to support the car by stronger metal and spreads out the load to the frame/chassis more evenly. You'll just have to be careful and creative with how you lift your car.