A used 110/74 crank, in good shape, is $20-50 on eBay.
How is that too much? Even a new Sugino at $100 would be worth it if it'll make the bike work.
I simply don't understand the thought of approach that you shouldn't spend much money on a bike if you can't get that money out of it when you sell it. That approach completely ignores the fact that you benefit from the changes while owning the bike.
Keep the old crank and slap it on when you sell the bike, and keep the nice newer 110/74 for a new bike or build.
The claim that you will be spending g more than the bike is worth is a good approach for some beater, perhaps, but not for a bike that will be used to ride down a coast and more. You should want components that work for the job you plan to do, while keeping cost in mind. A $100 crank is hardly more than the bike is worth.
Iconic classic touring bikes aren't the only ones deserving of upgrades.