340 crankshaft info needed

Ok, I have removed the oil pan because of unknown bottom end and no harmonic balancer with engine and too many variables
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Pistons are KB silvolite 1267-060 cast pistons (10.2 CR with 65cc? heads), and crankshaft unfortunately is a non 340 cast 2658278 with no hole through the rod journals, and 1618699 LD rods, but I do not intend to spin this thing up to maybe 6k rarely - will this rotating assy be ok? I assume so....
what balancer do I need to use on this crankshaft?

The heads are small valve 587's, but fresh with all new valves I do have a pair of J small valve heads which I am considering maybe putting 2.02's in? what would be the ad/disvantage to doing this.

I am considering maybe a 284 484 cam and will be using early hp manifolds. again 4-spd trans.