I'm rebuilding a 318 engine that I don't know the history of. The block casting is 2536030 ('67, 0.030 over), the crank casting is 2658393, and the connecting rod castings are 2406782. It's all been to the machine shop and cleaned up. Rods have new ARP bolts. I weighed the the rods (with bolts, but without bearings), and the lightest is 724 grams, the heaviest is 736 grams. I did not build a jig to weigh the large ends and small ends. Pistons with rings have a 2 gram spread. My scale has 2 gram resolution, so I know if I do anything myself I need a better scale first. How bad is a 12 gram spread? Is this worth having the shop balance? While I'm trying to do this right (the operative word there is "trying"...) I don't want to spend money needlessly. I'm not building a 10 second car here, but I'd like to leave myself some room for improvements down the road. Thanks!