Need some advice. Have a 645 lift cam, dual springs (1.550 i believe) on Dart Pro 1 Heads. My 3/8 pushrods would not work completely. On first two cylinders I found 3/8 was good for both exhaust valves, not good on both intake valves. Due to head, it will not allow the 3/8 rods to work with proper clearance on the intake valves. My test pushrod is 5/16 and it worked just fine. According to the Dart head document that came with the heads, it stated must use 5/16 rods which explains why the heads came with 5/16 guides. So my question is if i downsize to 5/16 chromoly rods, will I be ok with the information I've provided above? motor will only be used for drag racing, turning around 6500-7000 rpms.