Lots and lots of people have been where you are.
I am currently, and from what I can tell, it is my clutch for the clutch fan. When my temps were at almost 230* today, I could spin the fan with very little resistance. If your clutch is pulling the same problem, it doesn't matter what the fan is "rated" at because it isn't actually pulling what it should.
The MKVIII fan will flow some serious air, and it should fix most of your problems, with the only problem being that it pulls almost 40 amps, at full tilt and that is a lot for one item considering you still have a stock alternator. An alternator that is rated at full sing at like 60 or 65 amps. You need to upgrade your alt. Especially considering the instant start spikes going over 100 amps. Not good for your puny stocker.
There is not a very easy way to measure the stock fan CFM, but from what I understand the MKVIII is capable of over 4000 cfm, with some people suggesting over 4500. It moves some serious air, and has proven time and again it can cool boosted plants. If I were in your situation, I would put a PA Performance 130 amp 3G alt or like I have a 200 amp one so I can have my stereo loud, electric fan, a/c on high, and be idling in traffic. I know it is overkill, but not replacing something twice makes me smile. I would then get something like the DCC controller, or a Flex A Lite VSC, and either the MKVIII or Taurus fan (pulls over 3600 cfm and less amps) and that should fix your issues.
1993 Notch HCI /1994 Lightning / 1973 F250 Hiboy/ 1986 Omni GLH /
1994 Cummins 3500 / 1997 Cummins 3500 /1980 F250 6cyl