Assuming you do all the work yourself, the Merckx probably has the best potential as a flip. It'll depend more on the condition of the free than anything else, and you'll have to budget for replacing some parts, like the chain and saddle, and probably the tire's.
Bit should fetch a good price when cleaned up, especially if you can wait for the right motivated buyer. I think even $300 for the Merckx, with the rest tossed in as gravy might be OK.
Bit jts all about the cidition and detail specs.
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