Re: tilt/trim retrofit
I'm going to say yes. Back then trim consisted of a piston on either side of the engine and was probably a Merc aftermarket design idea to put trim on an engine design that was years old and wasn't initially conceived with trim.
I had an '84 85 Merc with this type trim and to the best of my recollection, it was feasible to remove the engine from the clamp bracket and install a different clamp bracket containing the lift cylinders....course you need the hyd pump also.
Find yourself a Merc dealer that has been in business for 35 - 40 years and he may have just what you want in his scrounge area....plus he will surely install it for you. I did that with a '72 OMC, course it was only tilt as OMC didn't put trim on it's engines till the next model year.
HTH
Mark