Since we don't need emissions checked on '91 vehicles here, I was

You need an intake manifold and carburetor as well as a distributor to make
the engine run.  Retrofit the older magnetic pickup distributor and wiring
for this.  I presume you can get the fuel pump to operate without the
computer?  If not, you can retrofit a mechanical unit, but, it's a big
retrofit, IIRC, it requires a specific camshaft and an eccentric.  I believe
these are Dakota specific parts?

The overdrive and lockup for the transmission can be controlled with
switches mounted within your reach in the cab.

As to the operation of the rest of the truck sans computer, I don't know.

We bought an 87 Dakota when they first came out, and had to get a '91
with Club Cab when our son was born.
Drove it for 240,000 miles and had a cracked block. Should have gotten a
new engine, but bought an '03 Dakota that my wife now drives every day.
Well, the guy I sold the '91 to had a new block put in and repainted it.
Drove great for 4 years, but now has problems with the computer wiring
harness, and might sell or trade it back to me.

Since we don't need emissions checked on '91 vehicles here, I was
wondering how much work it would be to rip that computer out of the
truck and drive it for another 15 years. Since it's a 318, I should be
able to find a manifold & carb. Would I have to get another
transmission, since it's controlled by the computer? The tranny's not
%100 anyway. What are my non-electric tranny choices?