Doing an alignment in the driveway on a 72 scamp

Just run a string line down side and square it of your rear wheel.
Give yourself 3mm toe in on each wheel at the front.
Make sure you lock the steering wheel from moving and position it in the dead ahead position while doing toe in.
You can get a digital readout level off ebay for cheap. When measuring your caster just turn the steering wheel 1 full turn and take your measurements, don't get hung up what the value is just make sure both sides are the same and it's positive caster.
And give yourself around 1/2 deg neg camber.

Remember to do your toe in last.

I've always done my own wheel alignments. They come out spot on.