Use it, it is a good part. Just recheck the installed height after a few runs to be sure you have it locked down. As the 6pack man said, welding in a plate under the car where the snubbed hits is a good idea. IIRC, that was mentioned in some MP writings a while back.
Do not bother with a zero load yet. Work your way there. The 1/2 inch measurement is a great starting place.
The originals were designed with the S/S springs being used in the day. This is why there a very tall item. I have and I like the part you pictured. Super adjustable.
Are these any good for track use? The originals don't look as 'adjustable'.
What would be a reasonable distance setting to the floor as a starting point?