If using 55 gal SS barrels for 750 gal syrup, that only a little over 13 barrels, hardly enough to make a tractor trailer load. While new steel barrels lined with latex and then using a food grade liner might be OK, barrels from a recycling center has no guarantee the barrels have not been contaminated with something else, I'd shy away for that reason.
In case you do end up selling some bulk, contact a buyer now (or more) and ask them what barrels they will accept, we can guess all day long, but with tighter controls all the time, only the buyer can answer the question, and that answer will only be "as of today", it might change tomorrow.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.