My 360 Magnum is sick

I do,Z. Go the Hughes 1110 springs,matching retainers. This will give you 110 on the seat,320 @.500. The retainers bump the lift,good to .530,.540 safe. Iirc,you have 4.10's out back. Would start there. Spend the money,Napa/K.D. valve spring tool. Anything else fails. Pick up the matching,spark plug adapter. I pulled rhe Schrader valve,out of my compression gauge threaded hose. Worked out nice.