Here is a few photos of a recent "Frankenmerc" motor I built. I called it a Mk-28.5 or also "Project 50:1" (There are parts from 50 different motors in this, to make 1 motor.)
This motor was built on a 1956 Mk-25 tower with a KH-7 drive shaft that I lengthened 7/8" It has a 1964 Mercury 200 powerhead and lower cowl with a Mk-28 top cowl. It has a 1972 tiller, and a Mk-30 saddle cover assembly. A lot of different parts in it, spanning 20 years of Mercury technology. My goal was to make a motor that might look like something Mercury could have come up with. Here is a photo during mock-up.
Steve