Well if it's got what you've described it is definitley a CFI, dont worry tho we've had no troubles with our CFI wagon, it hauls ass for what it is, it can beat a stock VL sedan so I dont see why it couldn't handle anything that can fit in a wagon, my mate has a CFI wagon and hauls around a huge 19' boat on the back of it.
From what you're saying it sounds like a good buy, there really is no difference between the 3.9 and 4.0, they are basically the same thing just one has rougly 30cc more. Make sure you get a full mechanical inspection on it before buying tho, if it passes a mechanical inspection with no major problems grab it, it is really hard to find EA-ED falcons in good condition for a reasonable price.
Phat Drift Damaged
Cobalt Blue 1994 EF XR8 5 spd
Fully optioned - Sunroof, cruise, body kit
Stock as a Rock for the moment