This is the one I have, I have done a lot of pots that were ~100 lbs. with no signs of strain. I paid a bit more when I bought it at Walmart.
With a dutch oven from Harbor Freight coming in at less than $25 with the 20% off coupon.
https://www.harborfreight.com/catalo...f&q=dutch+oven
I think there are other places online with similar prices. Full as it can be and still stir is over 100 lbs. Side "ears" allow picking it up with heavy gloves to pour out the bottom of the pot if desired. The bail can be used to move also but be advised the bail wire pulls really hard as do the ears and are almost same temp as the molten lead. Use really thick insulated gloves because the weight presses the hot metal against you and compresses the glove. You don't want to find out the fastest way to set down 50# of lead (drop it)
Cut some small angle iron to drop in and you can support a smaller thrift store steel or cast iron pot, not aluminum. Aluminum can fail under weight and heat of melting lead. So if your burner comes with an aluminum pot don't use it for lead. It can literally stretch and pop out the bottom from melting a pot of lead.
In my opinion the biggest advantage a propane tank pot has over a cast iron dutch oven is steel will dent if dropped and not crack. Steel tank also won't crack due to sudden temperature change. Cast iron heats evenly, and has a lid, and is ready to purchase off the shelf for a good price. With side handle ears useful to tip the pot or shift on the burner.
I think a DCrockett over in vendor sponsors is a member makes and sells the propane tank pots. Not off the shelf but might be an option if you wanted to buy a cut off tank pot.
http://castboolits.gunloads.com/foru...endor-Sponsors