The final Marauder variant was the XB-26H. It was actually a TB-26G-25-MA (44-68221) that had its original tricycle landing gear replaced by a set of tandem mainwheels that retracted into the fuselage. In addition, a set of outrigger legs were added for lateral balance. The fuselage had to be externally stiffened to take the additional landing loads of this tandem undercarriage.
The XB-26H was known colloquially as the "Middle River Stump Jumper" and was part of a experimental project to test the installation of the landing gear proposed for the Boeing XB-47 Stratojet and Martin XB-48 bombers, which were then on the drawing boards. Flight tests were carried out in May/June of 1945 at the Martin field.