Since you seem to be good at fabricating……
Four pieces of aluminum angle.
Vertical slots cut in two of them, bolts, washers and locnuts for the others. Use this to adjust the engine height of whatever engine you choose.
On the outside you will want to do plate aluminum to be used as a stiffener for the angle pieces then wood on the outside and whatever you like to seat the transom clamp cups against on the inside.
This one is made a little different. With the one described above the height adjustment will be on the sides.
Notice the difference between two different short shaft engines. The Speeditwin required the jack plate be all the way up.
The 3-cylinder 25 only likes to be about 1.5" above even with a modified prop.
NO two engines will be the same and every prop you change should require small changes as well.
Yes I know there is cutting board on the outside of this one and that is slippery. There is a bolt and nut between the transom clamps on the square tanker and I through bolt the 25hp.