I've never heard of a 24 valve failure but according to a mechanic at Cummins NW the old style cover was used on some of the '98. 5 and '99 24 valve engines, though the pin fit problem was corrected.
For those who don't know here's the scoop on the KDP
Timing Case Dowel Pin
In the back of the timing gear case, there is an assembly index pin pressed
into a hole. Some holes do not fit tightly around the pin and the pin can
vibrate out of the hole, then fall into the gear train. The pin is then
rattled around by the timing gears until it either falls into the oil pan,
gets kicked out through the side of the timing case, or passes through gear
train bending the camshaft and ruining the gears and case. A small number of
12 Valve engines have encountered this problem but the repair is very
costly.
Response from Cummins on this matter
The timing pin diameter from the supplier and the hole drilled for the pin,
are designed to be 'press fit' dimensions. In some rare cases, the supplied
timing pin dimension and the drilled hole dimension, may not provide the
correct 'press fit'. During assembly line manufacturing, it is impossible to
determine the amount of 'press fit' between the pin and the drilled hole,
once the pin is installed into the bore.
A few of the pins have not had the correct 'press fit' in the drilled hole
and have worked out of the hole. This does cause extensive damage to the
gears and gear cover. The percentage of failure is very, very low and did
not justify a major campaign of all engines. If an unexpected failure should
occur during the warranty period of the engine, the repair will be handled
under normal warranty practices.
Early in 1998 the gear cover was changed to a 'blind hole' design, which
would not let the dowel pin move out of the bore. If you have a great fear
of this pin coming out, we suggest discussing this issue with your local
Dodge dealer or Cummins distributor, to determine the appropriate action in
each situation.
The pin itself can be replaced if desired or Locktite can be used to hold it
in place, without having to replace the pin or gear housing assembly.
We hope this helps you understand the dowel issue better.
signed Cummins
Attention: TDR Forum Junkies 
