I'm working on my 30 hotrod and orginally went with a reverse eye stock rear leaf with a few leaves removed. I know I have no weight on the frame or in the body but it's still too high in the back for my liking. I purchased a model T style spring to see how it does. I hope to get a few inches in drop.
Take the wheels off or pull the rear end out and set the car up on blocks at your desired ride height. That way you have a number you know you are shooting for. There may be a frame Z in your future.
That totally weedy, tiny thread on the little tie rod end used to locate the front bone. All there is between power, weight, brakes and disaster. I would re-do that with much beefier parts. And ensure the bracket has strong gusseting to boot.
Does that Speedway spring have the same width to fit into the original perches? It says it's for T buckets.