Forged 340 Crank in a 5.9 Magnum

TT5.9mag said
And wouldn’t make much difference.

junkyardhero said
but you sure could brag about having a forged tree-fordy crank in there and the bill from the balancing shop to prove it!

Never said it would make much difference. Just that you could. And the "Bill from the balance shop" wouldn't be necessary because they would have the same internal balance as the stock 318 magnum crank had. And before you say '72-3 external balanced version 340 crank, those weren't forged no more. Those were cast.
Honestly I was looking something up once I. A crank kit book at a car quest some years ago and I kid you not the crank from a 318 went from at least 1967 (maybe earlier, ) to well Into the 90s. Same crank casting number. So no rebalance would be needed. Actually there were some 318s built in the 70s with forged cranks/ although not many. These were HD truck and industrial ones.
As far as the original question it wouldn't work because the 360s always had a bigger diameter main bearing than the 273-318-340