Linkage set up on 1974 Plymouth duster with 318 automatic

I just recently purchased a 1974 Plymouth duster with a 318 automatic. I purchased a Holley four barrel and installed it on the car. I am concerned about the existing linkage and don’t want to damage my transmission driving it. The Short distance I drove it to test the carburetor, I noticed the car hesitated shifting from 2nd to 3rd, and seem to downshift into second while coasting to a stop. (Like pulling the gearshift leverdown to second). Any advice on linkage set up would be appreciated.

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