I run a 13 lb cap in my Mercury.  I can't speak to whether or not your system will support 18 psi or not.  Remember that extra 5 pounds of pressure is working on large surfaces of many dozens or even hundreds of square inches (expansion tank and rad tanks), and as such will generate many hundreds or even thousands of extra pounds of force.

We had a handfull of them when I managed the Testing Group at a ATV and Side-by-Side OEM.  Used them to jump start ATV's that had been sitting out for a few months, normally in the dead of a Northern Minnesota winter.  They worked well for that.  However, the packs never seemed to have enough oomph to light a frozen tow truck off though (Chebbie Dirtymax's).

I wish we would quit calling it AI.  It is very far from artificial intelligence, at best it is an extension of industrial machine control algorithms (PID control loops in particular) which date back to the 1920's.  The difference is that these programs are searching the internet at incredibly fast speed, compiling the relevant information (snippets of text strings that contain key words) from previously written documents and generating an output within the predefined error bounds.  The programs are unable to process context, which is why the articles seem so poorly written.

I think the vast majority of cam failures that you read about are caused by or are due to problems other than the cam itself.  Wrong valve spring rates, bad geometry, break-in oil, contamination, etc.  Most internet warrior engine builders don't know the first thing about root cause analysis and it is much easier to blame the cam manufacturer than get to the actual root cause (or admit you f-ed up to the whole wide world). 

I would not be afraid of any of the name brand cam manufacturers.  I have had good luck with Elgin, Howards, and Comp in a wide variety of engines.  However, do the math.  Just because Comp says to use Valve Spring XYZ, that may not be correct.  They have very general recommendations that are based on much better selling engine platforms than the FE (I.E. SBC, LS, Windsor V8, etc), that may have very different geometry considerations. 

On the other hand, I had Oregon Cam Grinders regrind the cam for my 7.3L IDIT (try getting Comp to make you a cam for that particular engine...).  They did a great job, and the cam works great, and the engine runs great with it.  I have no trouble recommending them.

I bet those Ford 318-340-360 cylinder heads are rare as hen's teeth. 

It amazes me how these auction companies can miss on this stuff, especially with the instant access to the internet these days. 

I am not much of a brand guy.  Normally I just go to my tire guy and say vehicle X needs new rubber, what do you have?  That said, I run 15" Hankooks on this not-so-little lady.  This set has 7 years and about 35,000 miles on them and have worn very evenly.  I chose Hankooks because they were one of only a couple manufacturers still making pinner whites.

The horsepower expectations are directly related to the thickness of your wallet.  I.E.  How fast do you want to spend???

EFI doesn't produce any extra horsepower, it is just a more efficient and arguably more precise and tunable way to introduce fuel to an engine.  Horsepower is directly determined by how much oxygen you can shove into an engine, and therefore how much fuel you can efficiently burn.  Tell us about the combination.  Compression ratio, induction (NA vs. Forced), cam profile, head flow, RPM range, etc.  Then we could offer up some expected performance numbers more precise than somewhere between 200 and 600.

Sold!