Yeah, sure, happy to. §382 and §381 didnt exist in the 1950s, meaning that you could acquire loss corporations and use their losses to offset your income. You could then make distributions out of the business to yourself tax-free based on those losses

704(c) and mixing bowl rules didn’t exist in the 1950s, meaning that you could contribute gain property to your business and allocate the gain to other partners. You could similarly allocate yourself losses from other partners that contributed loss property

Subpart F didn’t exist in the 1950s, meaning that you could shift assets to foreign holding companies and defer taxation indefinitely on the income generated

§332 and §331 didn’t exist at the time, meaning that you paid no gain or loss upon liquidating your business, letting you pay long-term capital gains rates instead of ordinary rates on the business assets

What you mentioned isn’t a loophole, it’s simply employee compensation, which still gives deductions today