How hard (and expensive)is it to convert a manual transmission to an automatic in a '74 Ford F100 (2wd).

Would it be easier to just get a different truck?

I don't know much about Fords, but here goes: It's a hell of a lot easier to go from a manual transmission to an auto than it is the other way around. If Fords are anything like Chevys, you'll need a flywheel for an atuo tranny, and you'll also need a shorter driveshaft since an auto tranny is much longer than a manual. You'll probably also need a new transmission mount. For a shifter, I'd get a cable-operated after-market (it will greatly cut down on the PITA factor). You can keep the same pedal set-up, just cut off the clutch pedal. All in all, it isn't really all that difficult, expensive (you can get most parts needed at a junkyard), or labor-intensive. If your truck is still in decent shape, keep it, and switch trannies.

Would he have to worry about wiring up any emissions sensors, etc.?

The good thing is that at some point soon, there is some smog exemption.  The DMV web site could tell you what years, etc. Gene.  You might be exempt already.

It is a 74 so it should be as easy as changing your tranny.
You will need, at the very least, the donor tranny, the linkages, and I would take the shifter, or you can get an after market shifter for the floor in place of your 3 or 4 speed stick.
You may need the flywheel and the harmonic balancer off the front. You would have to check the interchange and balance between the two. If you get it all from the same model and year truck as yours, you can get the transmission mount bracket and the driveshaft and you should be good to go.
Way cheaper than getting a new truck.

i've not actually done the conversion on a f100 series, but can tell you that there are a fair number or variables that may or may not make it complicated. depending on what you want, you can spend a ton of money or not. keep in mind that nearly anything can be made to work with enough time and money.

the transmission that ford used for its autos in that year was the c6. there are a ton of them out there and rebuild kits are cheap. 150.00 or so. but depending on your engine size, the proper bellhousing could be an issue, and also the drive shaft length. you can use an aftermarket floor shifter...or maybe one from a ford pinto with a little work. if you try to piece the thing together it oculd be a pain in the ass. neutral safety switch. kickdown lever. wiring issues.

by far the easiest thing to do would be to find a donor f100 with the same engine as yours, auto tranny, and 2wd. and jsut swap the whole set-up.

your budget and skills and desire to do it yourself will determine how much effort is involved. however, there may be a conversion kit out there from a 4x4 supplier that has everything you need already collected. perhaps someone with more f100 experience will know.

hope that helps.

Don't forget about the rear end. Autos are usually equiped with a ring & pinion that has a higher gear ratio than a standard. The ring & pinion will need to be swapped, or the whole rear end.

I'm going to argue with you on this one, 2manytoys.

Regardless of whether you started off with a C6 auto or a standard 4 speed, the final output of the transmission is 1:1 or direct drive.  While you could order several different final drive ratios in the axle, they were not directly related to the transmission.

Next question:

My '74 truck has a 300 cid [u]6-cylinder[/u].  Some day I may also want to upgrade to a V8.

If I put an auto tranny in this truck (with the 6 cyl.) will it also work with a V8?

TIA !