Check out my pics on the lid problem size wise:
Can't see too much on the thrid pic, but if you look close enough on the first and second pics you can see where I tried to mash down the lid so it would fit. It did but I didn't like that it just sat on top of the barrel rim. So my fix was to add 4 skinny bolts and some furnace gasket to make the seal and keep it from falling or moving on the drum.
Oops no pics of gasket so here it is:
Here you can see the aligning bolts and the gasket held on by high temp red silicone engine gasket maker stuff.
Hope all this helps on a solution......