I used Vinegar to run through the cooling system on my model A and cleaned out a bunch of rust. I ran clear water through a couple times then filled with Antifreeze. It was good for that. I watched a ton of YouTube tests of vinegar, coca-cola, evapo-rust, and a couple others. I settled on evapo-rust. I got a 5 gallon bucket on Amazon for less than $80 delivered. It just works faster than everything else and can be reused. Molasses brushed on and covered with plastic wrap was a second choice and may work really good on large areas where soaking isn't an option due to size.
Dan J Parker/Elizabeth Colorado 28 Ford Model Roadster (restored) 46 Chevy 1.5 Ton Grain Truck being converted to a Pickup Street Rod "square nuts" started Oct 2017 follow my blog of the 46 project at squarenuts.wordpress.com