the s5 cams are killer in a de. but i'm surprised you're trouble free with them. grab a 4 ccw ve crank, use stock de/ve rods, acl main and rod bearings. last i checked, the sr16 pistons were on "in-definite" back-order so go with 12.5cr 87mm cp pistons. you can get them for less than $500 (shipped) in the lower 48. pm me for details on the pistons if you haven't already purchased.
i loved those S5's, i'm not surprised you eat vvl motors on stock cams
good luck, man. hope to hear more on your big cam'd de racing adventures