Cams How do you choose one?

You may get away with one or two sizes bigger than stock, limiting your lift to whatever your heads are set up for. After that your 3.55x2.66 starter gear is gonna be a pita, and the pressure loss is gonna show as less performance below 3000 rpm; plus those skinny 215s are hopelessly undersized even for the stock cam..
My 2cents is to drive that beauty the way it is first, and maybe put some meat on the back... first
.............................. cuz you know that 3000rpm in first gear is gonna be 24mph.
So if the current engine cannot initiate a good spin now, it's only gonna get worse with a bigger cam. With no other changes; the bottom end NEVER gets better with a bigger cam. With a manual trans, you have three choices; 1) for free you are gonna have to rev it higher and/or give it more gas to get moving. This helps you nothing at 30 mph. 2) the next cheapest is more rear gear, about one gear size per one cam size will keep you close to par. or 3) pump up the Dcr. This makes the sweetest difference.

In Lethbridge you are at 3000ft elevation so that sucks your current Dcr down to ~6.64 and the VP into slanty territory at 101VP. This is really soft to start with; because of your elevation. This is softer than a teener at 1000ft, and softer than a 225 at sealevel.
What I'm saying is you cannot afford to give up any, ANY Dcr!, so I wouldn't cam it at all, until you are ready to pump up the compression.
For performance,at or near sealevel,you want your Dcr to be closer to 8.0.
In Lethbridge , probably closer to 8.5Dcr. After that, the bigger cam is likely to only increase your performance somewhere after 4000rpm depending on what you chose. And 4000 with 3.55s in first gear is 32mph, so it better spin a bit else you are gonna be waiting. And you are still gonna have to slip the clutch out.

Here's an example If you pumped the Scr up to 10.5, you could run an Ica of about 64*, to get a Dcr of 8.4 and pressure of 158psi with a VP of 133VP. This will run on pumpgas at 3000ft, just don't be taking it too much lower.
So what cam can get you 64*Ica? There's a bunchof them. The biggest perhaps would be a 276/110, what I run,and she'll smoke those skinnys 'til you lift, or 80/90mph if you dare not to. But that 276cam sucks gas and is not very street friendly,and you can't parade with it cuz about the slowest you will be able to drive it is ~5.5 mph, after you have tuned the nuts off it. This is about a [email protected] cam.
For your application VR suggested a [email protected], a good torquey choice for 3000ft. This one might be a 258/266/110, and lets put it in at 106 so it will have an ICA of around 55*; great we can do that with less compression. Let's set it up for 2000ft so you got a bit more wiggle room. Ok I get
9.7Scr/8.27Dcr/160psi@144VP@2000ft...
Now at 3000 ft the pressure drops to 155@140VP, and there you have it!
This will idle down to 650 and drive no slower than 5.1mph, so parading is still out, unless you don't mind roasting the clutch.
140VP represents a lot of performance below 3000. I think it would make a good cruiser. With a really good first gear romp. And your current gears will take that 215 to ~38mph@4800rpm, before it runs down the back of the power curve, but you will hardly notice it mostly cuz you will be spinning those skinnys, and it will still buzz up to 44mph@5500 no problem,with the right springs. And you have a bit of headroom to go down to 2000ft on perhaps 89 octane and 1000 on 91 . I am at 930, so you can come to Manitoba and visit me.

For you; if you want close to the best out of your combo,cylinder pressure and ICA are gonna have to be very carefully matched to stay out of detonation troubles.
There is one other option; aluminum heads. Now you can really make pressure, and if you do it right running up and down to 3000ft won't be a problem.
But with iron open chamber heads 160psi is nearing the limit......