comp cams 995-16 are what is recommended as springs for there line of solid-cams . available from summit for around 100$ a set of 16. they migth require the use of teflon seals- and therefore machining the heads- as they are true double valve springs. i think that with the mopar 528 cam you need to have the heads machined anyway - need to cut the valve guides for retainer to guide clearance- so the 995 seams to be the cheaper alternative, even compared to a single valve spring.