High Compression 390

So do I understand this right; the truck will be running from 5000 to 9000 feet altitude?
If yes, 11/1plus is peanuts for a small cam and aluminums, which is what you need to haul stuff with.

From 5000 to 9000 your cylinder pressure will drop about 20psi, a huge drop. In fact, with 11.3SCR, your pressure may fall to just 150psi from just 170, with an ICA of 62*,a small cam of say 262/112
So you can already see that 11.3 is a necessity with that cam, not an option, cuz at 150psi, your 390 is already being strained. If you're hauling a load, she's gonna feel it.
So in your case you need a 20psi range, and you might as well run it up to 185psi at 5000, so it only drops to 165 at 9000.
Using that same 262 cam, this would require about 11.8scr at 9000 to get 163psi; which would increase to 185psi at 5000ft
The ICA becomes somewhat critical. Therefore to make power you are gonna need the fastest ramps around, which points to a solid lifter cam.
That 262 cam in a HFT will be about 216 at .050.
A 262solid FT might get you a [email protected]; about 70% of the next bigger cam.If you get a proper 4speed, you can tighten up the LSA to say 108, and then you can run another size bigger cam say and maybe get about [email protected]., still with the 60/62 ICA. That would be 11* bigger but the overlap jumps from 41 to 56, a very significant increase.

On the flipside, you could run a smaller SFT for a smaller ICA and then you could give up some Scr.
Say you were happy with a [email protected]. This could be a 258/266/108 cam with an ICA of 55*. Ok that would take an SCR of 11.4 to make 163psi at 9000ft. Now at 5000, that same 11.4 would make 184psi.
But the 108 cam will not play nice with the NP435 wide ratios. Those 50% splits means if you run the tach up to 5400 say, at the shift, the Rs will drop to 2700, so you have a powerband requirement of 2700rpm. That will take an automatic type cam to cover, like a 115 to 112 LSA. Whereas the A833 will have a powerband requirement of just 1500. So you can run a 108 or even down to a 104Lsa with that..... and that would decrease the ICA again, which would allow a lesser Sca.And if you wanted to, now you could go back to a hydraulicFt cam.
Bottom line is.... IMO..... to get rid of that NP435, and get you an A833, that has splits of about 72%, instead of 50%. That is the whole point I'm trying to hammer home here.