For boosted, you'd want the 90mm. You can use any MAF/Injector combo - BUT...
Different MAFs have different transfer curves. A MAF will measure "x flow" at 4.7v. That "x flow" roughly corresponds to "y HP". So, a stock Ford MAF will support up to ~300 HP. AN MAF will support more HP. But, you loose some resolution at low air flows (idle).
If you go to the "42
ADJUSTED" "Fox" MAF, by *definition*, the output of the MAF is ~45% that of the stock MAF. At low flows you then loose a LOT of resolution (less than half).
The 96+ MAFs have a different transfer curve. So, they are more accurate at low flows (for idle and emissions). But, their curve is less accurate towards the top of the curve.
Now, it gets more interesting. The LMAF is BY FAR, the most accurate Ford-style MAF you can get. The *curve* being less accurate in the top is MINOR compared to how ACCURATE THE MAF MEASURES THE *REAL FLOW*!
Also, you have the issue of how accurate any MAF is to the base-line. This isn't an issue if you get the MAF flow-tested. However, EVERY MAF will vary in accuracy over temperature, pressure, and actual air flow patterns (varies because the air filter's restrictions vary over time).
So, even if you got some MEGA-POS C&L flow tested - BFD! IMHO, it would STILL be a worthless POS because of how inaccurate it is over varying conditions.
Go with an LMAF, or the NEW-style PMAS MAFs. The LMAF is the best design and will vary less over different conditions. But, with the PMAS, you get the flow-sheet. Still, for ~?$125? you can get your MAF flow tested (at least PMAS / ProM used to do that).
If you have a Tweecer and MANY hours to spend, you can fine tune your MAF curve for your actual SETUP in YOUR car.
That may have been a little more detail/in depth than you wanted.
Summary, GET THE LMAF!!