[Adger Smith]

With a low lift like you have and the low spring installed ht. you need a spring that has a lot more seat, like 200+ and a rate that is very tough ending up with at least 550 to 600 open. That may be hard to find. Then when you get enough spring you need a real stiff pushrod. Those engines have a nice short pushrod with good angles. I would use at least a .125 wall and if it will fit a 3/8 to 1/2 double taper .150 wall pushrod. You need to remember that a boosted engine has trouble opening the valves. The pushrods in an A/fuel engine that I've helped with look like drillpipe.
BTW those are just a good starting point for spring pressure. You could need more because of cam profile and valve/valve gear weight.