For reference for ya, I'm posting a pic of a recent 33 gallon tank install I did onna '74 sii.
That tank had the original bottom removed and then replaced with diamond plate, so it's 1.5" overall wider, and longer, on the bottom, the plate forms a distinct lip. I fabricated the strap mounts to replicate the oem mounts.
It's also one of the very popular aftermarket tanks from back in the day when this stuff was common, made by a major tank fabricator in portland, or whose name escapes me right now. Those tanks were marketed by many distributors for the Scout II when they were in production. It is virtually identical in design/size as the one currently available.
Though this particular rig doesn't have a receiver mounted, the universal-fit acme receivers I normally install on this stuff would have no impact on the 33 gallon tank fitment.
I spent many years in the towing products bizz, but have no experience with the curt brand as it was a regionally-distributed item and not generally available inna "warehouse" distribution system in the southwest where my wholesale/retail business was based.
But if you can post some pics of your receiver mounted on your rig, I'm certain we can determine if the tank swap would create any trickledown for ya. Thanks for asking about this, it's always better to check things out when dealing with parts like this so there are no surprises down the line...and it also adds to the knowledge base in general!