[Kenth]

There is no way 1969 RA III jetting #72 jets with 41-42 rods or 1970 RA III jetting #70 jets with 39 rods will work in a 7041242, unless the main airbleeds are altered to Pontiac sizes and the brass nozzles in boosters are replaced with the larger and longer Pontiac nozzles.
You will also need to replace the power piston as the Pontiac rods are not aimed for the APT system used in the Buick carb. IF you do all the modifications for running RA III jetting you might as well cut the stop pin off at the bottom of power piston to make this work.
There is more but i`ll stop here.

If the airbleeds in your Buick carb are untouched you´d be better off using the original jetting instead of hackning your carb further.
The only thing your carb would have needed from the start are a couple or three of thousands of an inch larger idle tubes and some CV, AU or CK secondary rods then it will work like a charm.

FWIW