Computer runs the fuel injection, and controls spark advance/retard timing.
So you are talking about switching to a carb and probably HEI distributor.
First issue is that there are no easy to get carburetor intake manifolds for the 2.9l.
I believe you can order them from companies in England, but haven't checked in quite a few years.
You can convert many distributors to HEI not sure about the 2.9l
In any case it would be expensive.
You may be able to build your own "tri-power"(3 carbs) adapter to use in place of the upper intake, but if you think fuel injection is a pain, multi-carb tuning is no day at the beach
, and you have to do it every month.
I guess the first thing would be to ask why you want to switch to a less reliable and problem prone system and pay good money to do it?
Carbs and distributors were 99% of the problems we had with older vehicles, the only reason some think "they were easier to work on" was because we HAD TO work on them ALL THE TIME, lol, so we just got better at it by shear repetition.
Computer controlled systems hardly ever give us a problem, but if they do, we feel frustrated because we often don't have the skill level, at that moment, to diagnose it.
Nothing wrong with that, we all learn new things as we go thru life, and usually only when we need too, lol, no one was born with the ability to rebuild a carb or diagnose a sensor problem.
The other 1% of the problems were and still are: starter motors, water pumps and alternators, wiz kids at Ford haven't got better versions of those yet.
Although the switch to all electric vehicles does solve all those problems, but will have a whole new set of problems we will have to learn to diagnose.
Granted, as we are 30+ years into computer controlled engines the earlier ones are going to have more problems, from wiring and device failures.
If you want to go with a carb and distributor your best bet would be a 302(5.0l) V8 swap with tranny, 302 was carb and distributor engine originally so there are many options.