In 69, the Buick GS's were all 350's, unless you had the GS-400, or the "Stage One", also 400 cu. in. GM wouldn't allow engines larger than 400 cu in in the "a" body (Shove-elle, Skylark, Tempest, Cutlass, and derivatives) until 1970.
The Buick engines only came with Q-jet carbs, and so have the spreadbore carb mounting pattern. That 950 DP would require machine work to mount on the factory manifold, but would work allright on the Offenhauser or Edelbrock manifolds available in the aftermarket. It would take a healthy 455 with stage one heads to make full use of the 950 DP, way too much for a log splitter, unless it's something like an Ed Roth cartoon!
My first car was a 69 GS-350. I eventually also owned a '72 GS-455, but was never able to assemble all the goodies to make a full "stage one". Those cars were real sleepers because not many people connected the brand Buick with performance.