Easiest way to run without using #3 is to run 1,4,6,7. The assembly will run very well (pull 4 wires off your V8 and try it!). If you try to run one bank only (2,4,6,8), the engine will not fire evenly and try to jump out of it's mounts. Many 4 cylinder KB hemis have been run this way with spectacular results (over 300 on El Mirage, Mike Wesche). Running one bank will require a custom crankshaft ($$$$). Some early V8s used a "flat" crank (Hispano-Suiza, Peerless), they worked fine on one bank.
Run 1,4,6,7, cut the big ends off the rods you're not going to use and bolt them onto the crank. That'll space the rods correctly on the crank journals and reasonably balance the crank. Or for a few $$ have some rods made that are double width on the big end, it'll give you a better bearing!