16 H big-end overhaul

You should be able to do the rebuild yourself - you will need to set up a Vee-block arrangement on your bench to support the outer crankshafts as you true-up the assembly, but with a simple clock-gauge tracking run-out, it's not difficult. 

Build up the crank assembly and nip up the big-end nuts, then torque one up fully, leaving the other one free-ish to set alignment.  Takes a while, but you should be able to get within a thou or so run-out with some gentle hammer time. 

I doubt whether 'balancing' will do much.  Build it as it is, and it'll be fine.