'91 Ford F-Series Engine Line-Up and Specs.

Engine Displacement     4.9L            5.0L            5.8L            7.5L            7.3L

Type and # of cylinders Gasoline, I-6   Gasoline, V-8   Gasoline, V-8   Gasoline, V-8   Diesel, V-8
Fuel System             Multiport EFI   Multiport EFI   Multiport EFI   Multiport EFI   Mechanical FI
Bore and Stroke         4.00 x 3.98     4.00 x 3.00     4.00 x 3.50     4.36 x 3.85     4.11 x 4.18
Compression ratio       8.8             9.0             8.8             8.5             21.5
SAE net horsepower      150 @ 3400rpm*  185 @ 3800rpm   200 @ 4000rpm   230 @ 3600rpm   180 @ 3300rpm
Net torque (lbs.-ft.)   260 @ 2000rpm*  270 @ 2400rpm   300 @ 2800rpm   390 @ 2200rpm   345 @ 1400rpm
Manufacturer            ?               ?               ?               ?               ?
VIN Code (8th digit)    ?               ?               ?               ?               ?

* 145hp @ 3400rpm and 265lbs.ft. @ 2000rpm for F-150 4x2 and 4x4 with 3.08 axle ratio