Whats the issue with re-using my rockers, rocker shafts and push rods?
On a very low-mileage, very clean engine this would be OK, but if your rocker shafts are already showing signs of ‘scoring’ (you can easily check by pulling back one of the rockers and looking at the underneath of the shaft) then it means your rockers are already contaminated with engine swarf (metallic particles stuck in the soft alloy rockers) so fitting just new shafts will only create new swarf to mess up your new short engine, so a new set is recommended.