Replacing a crank shaft questions

FWIW.. stock 340 pistons won't balance with a 318 crank; you have to add weight. But I doubt that the OP is going with old heavy 340 pistons.

That SCAT assembly is the easy way to go, if you want to upgrade and solve it with $$. Fair piston choices and they have a kit that probably has forged and cast crank options, internally balanced option, lighter SCAT rods, 340 mains, 3.58" stroke, Icon 360 flat tops in oversizes for .020, .030, and .040" overbores in a 340 block, and just under 10:1 static CR with the present heads if they have not been milled a lot.

I have not looked up the proposed cam but the dynamic CR may be a bit lower that optimum for pump fuel; that ought to be looked at before you make a move. But there is one ICON forged piston option with a dome that might make up for a biggish cam; the domes might need a bit of milling. (And only in a .020" oversize for the 340 block in the ICON catalog.) Knowing the chamber volume on your heads is necessary.

And there are 4" stroker options too. SCAT can often work with you to vary the options mix on their kits.