My 23 has a lifting mount, forgot what brand offhand (it is around 25 yrs old by now, as it came with the boat when I bought it used). I did adjust the angle by adding "thick washers" behind the mounting plate against the outer hull, to the top two mount bolts. I made these by taking some PVC (about an inch, maybe 1.5, diameter and about an inch or so long) and taping one end closed, then pouring in West Systems epoxy, unthickened. I then ground one end to a bit of an angle to more or less match the angle between the "verticalized" mount and the reverse angled transom, and obviously to the right length to angle the mount toward the rear enough to make it vertical (some trial and error there, does not have to be perfect). I then drilled holes through the center of each "solid rod" (well, I waited for the epoxy to harden first

) to fit the mounting bolts. You have to loosen the lower ones a bit then retighten to let it angle out. Not perfect, as the bolt heads end up not 100% flush with the surface of the mounting plate, due to the angle imposed by the use of the old transom mounting holes. It has worked for the 6 or so years I've had it, and the prop thrust is pretty parallel with the water now.
By the way, mine came with wood backing plates - I think it is 2X4's. Assuming you don't flood your boat and seal the outside well, this seems to work fine.
I think you can buy wedges, which would probably be easier.