I have built some, and a 400 with 5.700" long rods. No big deal if anyone may tell you what to look for. Clearencing the base of the block where the rod bolts are likely to touch the block is easy and obvious. The not so well explained part is the cam. The upper rod bolt (looking the engine on a stand, frontwise, the bolt that is on top of the rod) WILL HOT the cam. By a small amount but will. 2 ways to solve it: use a decent set of rod bolts like ARP, grind a little amount of the bolt head, the part that is hitting the cam until you gain enough clearence or try to see a powdered metal rod used in GM 383 crate motor or in the marine 6.2 litter engines like the ones from mercruiser. You'll get surprised by the small amount required. As for balancing, it is a must do, no way to skip it. But the use of a steel crank, like in the marine engines allows internal balance. Remember thou that the 87 and newer sbc engines are not internal completely as long as they do have an extra weight on the flexplate or flywheel, but they are all the same for all the engines, and since they do have a 3 inch bolt circlr, they may not be used on an earlier engine, the ones that have real internal balance scheemes.
