The engine is probably a 352, or at least that was probably the engine that it originally had. 351's came later, like around 1969 or 70 and actually had 3 varieties, the Windsor, the Cleveland and the M, all fairly different V8 engines. Any of them could have been swapped into your 67 over the last 40 years, but it probably is a 352,360,390 or even a 428, all of which look very similar from the outside and are members of the FE engine family. The odd thing about any FE is that the intake manifold is very wide and is part of the surface that the valve covers seal to.
The rust in the side seam is a real problem with the 67-72 Fords--it has happened to most of them I see. I don't know of a super good solution to the problem, but if I was going to try, I would wire brush out as much of the rust and seam sealer as I could and then treat the joint with something like POR-15 or Extend. Those products react with the rust and are supposed to stop it and seal it so you can paint over the problem.
Painting isn't that hard to do, but if you are not able to do it or don't have a place to do it, there are companies that do paint jobs fairly reasonably. Maaco is in my area, and I have read about other chains that advertise paint jobs for around $500. Maaco painted a car for me once, a long time ago and I was very pleased with the job they did, for the money. It still looks fairly good almost 30 years later.
I was less pleased with some of my body work. I did all the prep work, and used some body filler, which I had never tried before. It looked fairly good under primer, but when the final paint was on, that spot stuck out like a sore thumb. I wish I had done a better job. Anyhow, most of my sanding and smoothing of the factory paint seemed to be OK, although I got into a little trouble at the apartment complex because the sanding residue stained the parking lot a bit. The paint stuck very well on the car though, so my work was worth it.
These days many paint jobs are basecoat covered with clearcoat, rather than the single coating they used to do. I think this makes it easier to get a shiny paintjob. But the old way also worked fine, if the painter knows what they are doing and the prep work was done correctly and carefully.
If I was going to paint or have a vehicle painted, I definitely would first have it coated with a good primer/sealer that is completely compatible with whatever you plan to put over it. This step is really worth it, since the paint will probably stick better and small flaws will be covered better and whatever is underneath will not bleed through to your visible paint.
To paint a pickup halfway right, you need to remove the bed, so you can paint the back of the cab and the front of the box. But I have seen many repainted pickups where this wasn't done. Usually the paint sprayed in the opening between the cab and box does not stick well, since the area was not prepped at all. After awhile, it shows very badly, if you get close.
Another thing to consider is new seals and trim around the windows. Especially the ones in the doors, these tend to wear out and look bad. It is also very hard to mask them so they don't get some paint on them while the vehicle is being painted. I would plan to change all of that stuff after I painted my truck. That will also help with the leaks and wind noise.
If your factory paint is just faded, I would try buffing it out, or having that done. If the paint is basicly sound, buffing can make a vehicle look a whole lot better. If you do it yourself, be very careful and don't use too rough a compound, at least until you get used to using the buffer. It is possible to grind right through paint! BTDT
Good luck with your pickup. You should not have much problems at all finding parts for that model, one of Ford's best products, ever.