ive noticed several online outfits like jegs and summitracing dont give a specific length of pushrods for engines, is there any particular reason for this? i have a small block out of a 1980 C20, and was looking to replace the pushrods, is it best just to measure them and get a rough estimate of how long they are and just buy the closest length to those? or is there a site that gives the exact specs or does it even matter?