I think you have some numbers mixed up. The 5243A is a 10-gallon but is not associated with the model number you have preceding it. The SW6DE is a 6-gallon direct spark ignition.
Rob
U.S. Army retired
2020 Solitude 310GK-R
MORryde IS, disc brakes, solar, DP windows
(Previously in a Reflection 337RLS)
2012 F350 CC DRW Lariat 6.7
Full-time since 8/2015