Making a 55 Gallon mash tub

[Rclark12]

So I started talking about this in '55 gallon fermenters' but didnt want to clog that thread up since this is a little different. Im not talking about fermenting in a 55 gallon but actually mashing/converting the grains in one.

I have been wondering about using a 55 gallon steel drum with propane under it for large all grain mashing, as its annoying to do a bunch of small batches (my only other option is 5 gallon buckets an Id like to just bbang out like 30-40 gallons of mash in one shot).
OR
The other option is wrapping some blankets around a plastic 55 gallon drum andpouring the water over some grain and then adding the malt once it gets to temperature. I assume its ok to pour water around 180 degrees into the food grade barrels, and that with a blanket it would keep heat plenty long enough for a successful conversion.

I was searching threw here, google and youtube, found a few things on youtube and a beer site but not exactly what Im asking here, and haven't seen anything about using a 55 steel for a big mash pot which seems like it could work well, or atleast use it to boil water and I could use wood fire/coal to heat the water. Water could even just be boiled in the steel and transfered to the plastic with the grains in it for a two part kind of system. Seems efficent and simple enough. Thoughts on any of this?