Look at the C0 CFrames in my tweenOpen and tweenClose lines.
Leave your C0 as 0,0,0 at the beginning.
Set your Weld.C1 values to place the plow exactly where you want it in either the full up or full down Position which are just one of your goal values in the script in the above post.
Now tween your C0 from 0,0,0 to the difference between the C1 values you have in your lines above with the X value staying the same, the Y value to 2.771, and the Z value to -1.183.
If it worked right then the tweens will go from one position to the other and then back when reversed (you may have to switch the + or - signs in front of the values I gave since I don’t know the directional movement of your setup).
Then do the same with your Orientation angles. Seems strange to me you are changing the Y value by only .033° and the Z value by .046° though. You may just want to change the angles to (-19, 180, 0) and (0, 180, 0)