Here are the data sheets for the 51085(stock Jeep) 51515(stock ford) and the 51773(2qt ford)
Part Number: 51085 UPC Number: 765809510852
Principal Application:Chrysler/Dodge/Jeep Vehicles (91-06), Mitsubishi Eclipse (95-99); Caterpillar 3 Series Excavators, 9 Series Loaders
Closed Style: Spin-On Lube Filter Service: Lube Type: Full Flow Media: Paper Height: 3.790 Outer Diameter Top: 3.660 Outer Diameter Bottom:Thread Size: 3/4-16 By-Pass Valve Setting-PSI: 8-11 Anti-Drain Back Valve: Yes Beta Ratio: 2/20=15/28 Burst Pressure-PSI: 365 Max Flow Rate: 7-9 GPM Nominal Micron Rating: 20
Gasket Diameters Number O.D. I.D. Thk. Attached 2.834 2.462 0.200
Part Number: 51515 UPC Number: 765809515154
Principal Application:Chrysler Family of Cars/Trucks (57-70), Ford Family of Cars/Trucks (57-00), Mazda Trucks (94-00), Toyota Landcruiser (71-96) - (Two Quart version is 51773) 2/20=13/23
Style: Spin-On Lube Filter Service: Lube Type: Full Flow Media: Paper Height: 5.178 Outer Diameter: 3.660 Thread Size: 3/4-16 By-Pass Valve Setting-PSI: 8-11 Anti-Drain Back Valve: Yes Beta Ratio:Burst Pressure-PSI: 270 Max Flow Rate: 7-9 GPM Nominal Micron Rating: 19
Gasket Diameters Number O.D. I.D. Thk. Attached 2.834 2.462 0.200
Part Number: 51773 UPC Number: 765809517738
Principal Application: Ford Trucks, Massey-Ferguson Tractors, Oliver Tractors, VW Eurovan (93-95)
Closed Style: Spin-On Lube Filter Service: Lube Type: Full Flow Media: Paper Height: 6.982 Outer Diameter Top: 3.663 Outer Diameter Bottom:Thread Size: 3/4-16 By-Pass Valve Setting-PSI: 8-11 Anti-Drain Back Valve: Yes Burst Pressure-PSI: 225 Max Flow Rate: 7-9 GPM Nominal Micron Rating: 30
Gasket Diameters Number O.D. I.D. Thk. Attached 2.834 2.462 0.200
The 51773 has a lower burst pressure and a higher Micron rating. The burst pressure I don't really consider a big deal, if you are building enough pressure to burst oil filters you have other problems you need to worry about. I still consider the micron rating low enough, but not sure if it's worth the extra capacity or not.