1965 dart gt spring question

I might be able to get away with 3/4 of an inch, but if I take the spacer up to an inch have that much more room for precise adjustments to the shackles without running out of room. That and I don't want to string it all together just to find I needed more. I did do some measurements and based on the angle of the shackle now I would need just about 3/4 to an inch to put the spring eye in line with the shackle mount.