Personally I have never bought just a single rod, I've always bought them in sets, same with pushrods and pistons, just one of those things I was taught when growing up like not pissing into the wind, calling a cop who pulled me over 'sir', etc.
They do have 'master rebuild kits' for engines that come in various stages from a basic kit with all the gaskets, rings, seals then the next stage has that plus new rods, next one up has rods and pistons. You might be better off this way instead of mixing and matching, at least in the kit they will all weigh the same.
Same with valve jobs, I've never done just one intake or one exhaust, if I have the head or heads on the workbench I do them all.
It really sucks if you miss a crack after all that work..