UPDATE: this nice flattie is still available.
The Chevy 181 appears to be a 3.0 Liter Marine engine, which is likely a nice 4cyl for the jeep. This jeep is likely worth a closer look.
“1951 Willys Flatfender Jeep in great shape. Chevy 181 4 cylinder engine with a synchronized 3 speed transmission and split- stick transfer case. New 12.50 x 33 swampers with 410 gears and locker. 9,000 lb. Warn winch. $4200 (Best offer). For more information, please call (253) 208-6515 or (253) 884-8057”