80 gallon tank
I painted everything white because it is easier to see and work,
Do not drill through the top or bottom of the bus frame, just the sides,
The vertical piece bolted to the frame and the horizontal piece is 3in angle, the 45 degree piece is 2in angle, I used 3/8 in grade 8 bolts, after it was all up and level I then one at at time loosened the bolts and applied loctite glue.
I used a cheap rubber front door mat as padding under the tank and above the tank.
I used pressure treated wood to pad the frame to protect the tank, I also used the wood and mat above the tank since it is pressed upward against the floor supports
Since my tank is 5.5ft long I also added 2 supports to the middle, it has 2 end supports and 2 in the middle.
The 2 in the middle use a chain to come over the top of the tank, I used a long bolt with lots of washers to tighten the chain.
I used 2in square tubing bolted vertically to the inside of the bus frame as the top and bottom support anchor, probable a quarter inch thick,
Since the frame is 12in tall I cut the square tubing 18 inches long so 3 inches stick up above and below the frame. I cut 2 notches in each piece of tubing so it fits snug against the inside of the buses C-channel frame piece, so it cannot slip up or down,I then put 2 bolts in each tube to connect it to the frame.
These pieces were bolted to the inside of the frame because I would need to bolt the chains to these pieces after the tank was already hanging, not enough room to do it with them bolted to the outside of the frame.
To the lower end of the tubing I bolted a 2in angle piece that is horizontal and extends out under the tank, on the upper end of the tubing I bolted a chain that reaches over the tank and down to the lower angle piece.
I used that rubber mat and a thinner C channel piece of metal to cup the chain above the tank so each chain link cannot dig individually into the top of the tank.
You probable want one end of the tank to be lower than the other so when you hook up the end pieces for the first time use a single piece of thick plywood to place your level on for the tiny adjustments.
Several car jacks or several ratchet straps will help you lift it into place.
my bus thread, https://www.skoolie.net/forums/showthread.php?t=8860&highlight=bubb