In this post I will compare V10 and V8 Magnum rocker arms side by side. The V10 rockers are from a 1999 8.0 Magnum and the the V8 rockers are from a 1997 5.9 Magnum. Later model V10's upgrade to a 3/8 bolt from the earlier 5/16 bolt. The V8 uses a 5/16 bolt.
Rocker Arm Differences
The pictures below will highlight the differences between V10 and V8 rocker arms.
V10 and V8 rocker arm are identical in design but show dimensional differences when placed side by side. Both rockers are a 1.6 ratio arm.
The overall length of the V10 rockers is longer suggesting different valve train geometry to align the push rods for proper head clearance. Push rods will likely rub on the head gasket with V8 rockers installed.
The V10 rockers have a larger distance from the push rod cup to the point of contact on the valve stem. V8 rockers may work but have the potential to undesirably tip load the rocker arm. This could result in early valve train failure and excessive wear.
Width of the two rockers is very close and may be just variation in manufacturing tolerance.
Rocker Pivot Differences
The pictures below show the dimensional differences in the rocker arm pivot saddles.
The V10 pivot saddles have a larger radius and do not fit in the V8 rocker arms.
Showing the difference in width between the two pivot saddles.
Conclusions
V8 rocker arms will bolt in place of V10 rocker arm and may be a potential replacement for the discontinued V10 valve train. V10 rocker arms are still available but the pivot saddles are not. These typically wear out together and need replaced as a set. More research needs to be completed to verify push rod length, tip engagement, and push rod clearance with the geometry differences between the V8 and V10 rocker arms. Stay tuned for updates.