[blucar]

From my experience I have found that generally people confuse Sway Bars/Panhard bars with body roll bars.
The bar that Ford added to the front end of the DeLux '40 Fords is actually a bar to control body roll-up on turns. The bar that Ford installed on the rear of the '47-48 Ford/Merc's is a Panhard tracking bar to keep the suspension aligned with the chassis, ie; sway bar.
On the pre-42 model Fords, Ford used very short shackle bars, therefore there is not much need for a sway/track bar. The 42-48 had longer shackles, cars that had long shackles for lowering purposes could experience better control on turns with a sway/track bar.
My '36 has later model springs due to the '48 rear axle and '41 front axle with later model shackle bushings and shackles, therefore, a Panhard Bar is very helpful.