I think I might have a vacuum leak - and logically it seems like the easiest way to test is to label and cap EVERY vacuum line coming out of the intake/carb (Only spot vacuum hoses come out I think?).

If the car runs better, then install them one by one until it runs worse again.

To me, this seems easier than tracing all these hoses (Some of which I can't reach without taking other parts off) that I might not need to...

I don't think there's anything the car needs vacuum for when in park (Obviously I won't drive it since the brake booster isn't going to work) - or is there?

Is my plan flawed in some way?

 

Your process of elimination should work. Like you said, you won't be driving it at the time. I had a similar problem with my camaro. It drove me nuts. I had a vacuum leak, and the oil presure sending unit was leaking oil, so I thought. It turned out to be the rear seal on the intake manifold, which I only found on account of changing the cam, after switching everything else out (carb, dist, all new vac lines, etc..).
Vacuum leaks can be a pain, and usually are the culprit of other not so easily traced symptoms.

 

Yeah - I know.

Which is why I think I'll try to eliminate them as the cause of my problem before moving on to more difficult/expensive solutions.

With working 80 hours/week it's really hard to find time to fix my problems (Runs rough, crappy mileage, exhaust is rich enough that I could run my car off the vapours), so I need to do it in the most time efficient way possible...