The spring you should be using is a spring for a 455 stage I Buick. I looked at some of my motor building notes and the ones I have used in the past were TRW VS 1020. should be like 100 to 110 lbs on the seat with the valve closed, about 270 to 280 open at like .450 lift. I used the buick springs for a cam that was .480 lift and they worked fine no bind, and could take more but the higher lift does not get you much, the head's breathing ability peters out before it can use the lift, at least that is what my experience has been. Should have an installed height of 1.858. Not sure about retainers. I think the stock retainers will work but I remember using something stronger although I dont remember now what I used.
