Re: 1979 chrysler
If it was an engine originally equipped with a tilt/trim unit then there would be no reverse lock.
Centered below the steering snout just above the tilt pin you will either see a black lever--it may have broken off--or a white nylon plug. If it has the plug, the engine originally had T/T and it was removed.
NOW: You can replace the lever and shaft, it slides right in. You can get a shaft for the bottom of the yoke and a bent stainless plate which is spring loaded. A rod connects the lever to the plate and when up, it is released. When down, the plate engages the 1/2 inch tilt bar that slides in through the clamps. This keeps the engine from tilting in reverse.
CONSIDER looking for a trim/tilt unit. Once you have an engine with power T/T you will never want to be without it.
It is a really simple lock and I can't do it justice explaining. Unfortunately I have a B*tch of a time posting photos. Send me your email address in a private message and I will send a couple of photos.
Also, usually these parts corrode quite nicely into the aluminum and they are almost impossible to remove without destroying them BUT it is possible I MAY have a usable one.