Cam upgrade for my truck, '72 D200 with a 360

Well if your factory cam is worn out, (not likely at 128,000 miles in a big heavy4400# truck that goes zero to 60 in under 10 seconds,at 5000ft, strapped with the equivalent of 2.85 gears/6.98 starter gear);
then sure, you can better your power without loosing bottom end. But like I said, the power will be further up the rpm-band which is further up in roadspeed. To maintain the low-end power, your replacement cam only needs to close the intakes at or about the same time as the factory cam.
The best way to do this, is to start with a SOLID lifter cam, with which you can control the closing point by valvelash adjustment. Usually, the solid will have more .050 duration from valve closed, than a Hydro.
Typically, a hydro will have ramps from .006/.008 (usually called the advertised) lifter rise, to .050, of about 46 degrees. Few are less than .044. Many are more than 46*.
Furthermore, many hydros from .006/.008 to actually closed can be many many many more degrees. This has very little effect once the revs are up. But ........... with the equivalent of 2.81 gears and a stock stall, at what roadspeed does your engine come out of this? IDK.
Furthermore, many hydros are lazy on the .050 to .200.. With your combo, and your desire for power, you cannot afford to give anything up.

Now, A solid does not suffer from those limitations, because you set the opening and closing points with the adjustable valve lash. And since there is no hydraulic chamber to worry about, and the solid lifter is so much lighter, the rate of lift can be increased and so can the actual lift.
Normally, this type of cam can increase your power over the nose, without stealing pressure from the bottom-end. But in your case, at 5000 ft, if you're sharp, you have realized that this type of cam can be used to make the same power over the nose as the current cam does, but you can use it to increase your cylinder pressure and thus pick up power at low rpm.
Unfortunately, I don't think you will find an off-the-shelf, small-enough, solid lifter cam, to meet your needs. The theory is good, but I think that you will need a custom cam. by the time you get that done AND purchased/installed the adjustable gear, you could be close to the price of just installing hi-compression pistons, which is what your combo needs, and the which, will annihilate the weiner solid cam, with the 2bbl factory cam. At 5000 ft, pressure is or should be, your primary concern.
The Wallace calculator predicts your 2bbl cam (Ica of 56*) equipped 360 to currently make about 107psi@5000ft elevation. And the low-rpm power (below 3000/3500) is barely better than a factory stock 225 slanty at sealevel.
Performance starts at 130psi but doesn't really wake up until 140/145, and the best power will be achieved after 155psi. So as you can see, at 107 you cannot afford to give any pressure away.
If you had a 3400 stall or something, your pressure would be less of a concern, but 107psi is still pitiful.
Lets say the solid lifter cam has a 4 degree earlier closing intake, (now 52*); that will bring the pressure up to only 111psi.
But lets say you keep the 2-bbl cam and increase the compression ratio to 10.3. That would jump the pressure to 156psi@5000ft; A far greater power gain because it starts at idle/ zero mph.

As for me; I would not waste my time/money with camming this combo, with no other changes. So what! if you pick up 15 hp at 4600rpm; with your gears that doesn't show up until , ......... wait for it............. 48 mph. If the power march begins at 2hp@3400 rpm, that would be 34mph.

If anything, I would put a 3000TC on it and pick up say 40 ftlbs at 3000=23hp at ZERO mph; now that's what your combo needs. Ok well besides more compression,lol.
But to answer your question;
yes, it is possible to make more power over the nose without giving pressure/much pressure, away at the bottom-end.
But for less money spent, the TC will make you way happier.
Compare the cost of a solid-lifter cam and kit, plus adjustable valve gear, delivered and installed;
to the cost of a TC, delivered and installed.
Then compare guessing 12/15hp at 4600/48mph (one cam size bigger);
to guessing 23hp at zero-mph; (3000stall compared to 2200).
I know what I would do.