Got to agree with AK and Chris. Had the Iraqi military tried going up against the Iranians without the immense personnel sweeps and reshuffling in the Army and Air Force that the Revolution put into place, then they would've gotten hammered hard.
The US would've had no qualms against openly backing Iran, and F-14s and F-4s trump MiG-23s and -25s any day of the week. That's why the Iranians bought them.
Even had it happened, think it would've probably not been as large though. Saddam probably would've known he couldn't get away with much, and it might have turned into a second round of clashes like those fought over the mouth of the Shatt al-Arab in the mid-70s.
That way, inferior Iraqi numbers could be brought to bear on a single point where they might be able to make headway. I still don't think they'd be able to accomplish their goals (they didn't capture the mouth in '75, they lost it in '82-'83), but it's the only thing I could see Saddam thinking is worth taking a gamble.