Find a set of pushrods out of a '70's 318 motor and try them for a test.

Those wont work because they are a ball ball pushrods and those rockers require ball cup pushrods, so here is Comp Cams solution for this problem. length is 7.389 for the hyd cam and 7.497 for solid cam applications I personally have used the 7.389 pushrods with 273 adj rockers and hyd cams with no problems http://www.summitracing.com/parts/cca-7821-16