Since Water Wetter and Purple Ice are both essentially glorified soap, try a few drops (and I do mean drops) of dishwashing detergent before you pay the big bucks. Water Wetter is about $8... last I checked, a small bottle of Palmolive was about 89¢. It's a racer's trick from decades ago, from before either of the named products existed.
All three do the exact same thing: lower the surface tension of water so that it can better fill the microscopic valleys and pits of the inside of the radiator and engine (or pots and pans). That also happens to be the only purpose for soap. In a car it helps cool, in the sink it gets pans clean, and the Dial you use in the shower does the same thing to get you cleaner than water alone. Being so diluted, and under pressure, no, it will not get suds. Afraid of suds? Use liquid Tide instead.
And that's all for today's physics lesson.
Remember: if the car's summer-only, straight water cools better than water with "coolant". Best? Distilled water that's been boiled first, with a few drops of one of the aforementioned soaps.
As far as the fan & clutch, I was always told that when looking straight down, the fan blades should be half-showing in the shroud... i.e., centered. Otherwise, you get a turbulence condition known as "cavitation". Basically, the air gets pumped back on itself rather than through the rad and fan. Flow Kooler water pumps' "secret" is a disc on their impellers to prevent cavitation inside the engine... it works well, but I know two people who've had to replace a timing cover because the riveted disc came free. [smilie=e:
Once the car is warmed up in the driveway, say around 195°, shut it off and see if you can move the fan. If you can, change out the clutch, and while you're at it, get one with a long/shorter shaft to get the fan centered front-to-rear. Most parts stores have several shaft lengths, but you'll probably just have to go through the boxes.
When it comes to engine damage, it depends on the engine itself, but usually if you don't top 250°, you won't hurt it. The boiling over at such low temperature tells me you need more cap pressure, too--you should be running at least a 14lb, if not a 16lb. The higher the pressure, the higher the boiling point of the liquid.
Doing any or all of the above will almost certainly get you cool without the expense of a new radiator... but if you need one, the narrower-option (22") late-'70s truck rads drop in between the rails and are available with up to four rows. They're a little taller, but there are no clearance problems. You will need to drill a couple new mounting holes. If it's not enough, and you can clear it, get the 28" unit, which is still under $200 with a lifetime warranty. They look stock and cost about half of an aluminum unit... the 22" unit is [i]really[/i] the hot ticket for pre-'67 A-cars, where they fit well, and there's little other option.
