When the Alpina was introduced in 1971 as a playbike version of Bultaco's championship trials bike the Sherpa T, it was described as a trials bike with different geometry. The changes made it less focused with more range (bigger tank), a comfortable seat and higher gearing. The higher gearing came from the Matador, the tank got wider and more rounded as the capacity went from 1 gallon to 2 gallons....but what were the geometry changes? The recent acquision of an early seventies Bultaco parts manual provided the answers. Turns out both bikes shared the Alpina frame with 27.5 degrees rake.
The swingarm was also used on both bikes...
A different offset in the triple clamps would provide a different amount of trail but once again, shared components.
A different length fork would change the rake but once again...the fork is shared and from an earlier Sherpa T.
So it appears that an early Alpina is really a Sherpa T in different clothes.
I came across the info above on another blog. Just saving it for future reference.