The original sketches for the XB-36 back in 1941 had a twin fins at the tail, the same as the B-24.
A transport version had also been proposed and could carry 250 troops at a distance of 3,475 miles at an average speed of 300mph. Another troop transport concept was a double decker carrying 400 troops/passengers. A revised version had rear loading doors.
This was proposed before the XC-99 was ever thought of and the use of T34 or T56 turboprop engines for later follow-on versions.
Another Whiffer had an idea of a aerial water bomber or maritime surveillance.
A tanker version or weather reconnaissance.
I'm not too sure if the B-36 would make a good flying boat but it's worth a try.