There is an add-on trim switch that will retrofit onto older throttle controls to give you up and down control.
AFAIK there isn't separate functionality between trim and tilt, it all works or it doesn't.
I did this on a '78 Johnson 70HP and it's not too hard. Prop the motor all the way up. Remove the tilt assist cylinder, install Trim unit, run wiring to the trim solenoids and trim switch, install trim gauge sender, provide power from battery to trim solenoid box, and that should be it. Is this a single cylinder trim/tilt unit or does it have a center tilt cylinder and 2 smaller cylinders for trim? If it has the 2 small ones you'll need to get the stainless 'pads' that go on the motor bracket where the ends of the cylinders make contact. If it's single cylinder that won't matter.
