Not unusual to have hard shifts when cold. The softness of the shifts is
vacuum controlled by a "modulator vacuum control valve" on the aft end
of the injection pump.
The principal is: maximum vacuum at closed throttle, declining
continuously with throttle opening to no vacuum at full throttle. Soft
shifts on light throttle and hard shifts at full throttle.
So, if there's insufficient vacuum or a vacuum leak the shifts will be
hard. (Incidently, insufficient vacuum will also prevent engine shut
down, but that's another subject.)
After all these years the vacuum lines may be dirty and clogged - that's
a possibility that should be considered.