It's a matter of total weight and weight distribution due
                             to engine position. Assuming a small block V-8 is used,
                             light cars with the motor mounts 4" - 6” behind the axle
                             center line (33 - 34 Ford and 34 - 35 Chevy) usually
                             need 4 cyl. springs. Heavier cars (35 - 54) usually have
                             the engine mounted further forward, and generally need
                             V-6 springs, with a 1/2 coil cut to get the lower arms
                             level, if necessary. Big blocks, 50's pickups, and the
                             larger fat fender cars usually require V-8 springs.
                             Excessively heavy cars with Hemis, 460's, and pickups
                             into the 60's and 70's often need springs from an 82'-
                             93'5.0 Mustang, which are about I" taller and 15%
                             higher rate than MII V-8, but still fit MII mountings. The
                             basic rule is to get the lower arms level with FULL
                             weight loaded.
 

Mustang II Springs

         NAPA #277-3039 ('74 MII 4 cyl. w/o air)
     33-34 Fords, 33-35 Chevy

     NAPA #277-3036 ('78 MII V-6 w/air)
     35-48 Fat Fender Cars

     NAPA #277-3038 ('78 MII V-8)
     50's cars and pickups

     NAPA #277-3060 ('84 Mustang 5.0)
     Very Heavy Engines in 50's & 60'G pick ups -460,454, HEMIMustang II Springs

         NAPA #277-3039 ('74 MII 4 cyl. w/o air)
     33-34 Fords, 33-35 Chevy

     NAPA #277-3036 ('78 MII V-6 w/air)
     35-48 Fat Fender Cars

     NAPA #277-3038 ('78 MII V-8)
     50's cars and pickups

     NAPA #277-3060 ('84 Mustang 5.0)
     Very Heavy Engines in 50's & 60'G pick ups -460,454, HEMI