Who makes good oil pans for the SBM?

How much lower/deeper than stock is the 31590?

There's a fab shop near me...they makes lots of tanks for all sorts of applications, mostly offshore vessels and platforms. They even made the fuel tank for the Valiant in my profile pic. The owner tells me when they finish a tank and need to check it for leaks, they pour diesel fuel in it. He says it's the leakiest stuff on Earth lol.