I know it's a bad pic... But this is how most sump the rear 38 gallon tanks
FYI I would never sump a tank like that. Over time the vibrations that fitting experiences WILL break the steel around it causing it to leak. It's not IF but WHEN.
The proper way to install a sump would be to get one of the larger diameter billet alum sumps like what Bean's sells (they sell them for a reason).
Or, if you are set on building your own, start by welding a large diameter washer to the tank (3" or 4" diameter), then a smaller one, and so on, until you have a hole to install the bulkhead fitting. This will disperse the load across a wider area of the tank and essentially eliminate any cracking.