I have a new set of webers and an old set.

The new set are not as finished as nicely as the old set.

The old carbs have out-of-round throttle shaft holes. Can this be repaired?

The new carbs are 40 10A 3C1 2 J

The old carbs are 40 IDTP 13C1 1550

What model 911 were these old carbs intended for?

Also, the black plastic spacers between the carbs and head, can theses be made thicker to increase the heigth of the carbs for better top end performance. Or would you just install taller intake manifolds?. Are tall manifolds readily avaiable?

Is there any advantage [performance wise] to taller velocity stacks on the carbs? I remember in the old days these tall stacks were available for 356's.

Thank You.
Markus