A Body rear shocks

Contact ESPO and get what you need. They have exactly what your slant 6 Valiant needs.

Best advice right there. There is nothing wrong with the S/S springs for light to moderate competition. There OK for street use, but, not great. The absolute best bet IMO is to go to espo.com (springs and things) or call them up and speak with them. I have used there equipment several times and will again.