Hi guys. I'm doing some mods to my eb Fairmont. I've got a explorer manifold, gt40p heads,headers, 65mm throttle body and a 70mm maf from au. I have not started putting anything on yet. My questions are:
Will my factory ecu handle this without a tune?
Is it worth getting some 1.7 ratio rockers?
My car is auto. Can't really be bothered doing a manual conversion. Should I stick with the factory Cam?

You're going to need a tune with the bigger MAF (using a J3 chip). IMO get some quality 1.6 roller rockers instead, heavier double valve springs and a bigger cam. What about a hi-stall converter?

What condition are the heads? Most people will tell you to get some aluminium heads instead of spending it on the GT40Ps as they flow better.

What's your budget and how many km on your engine?

Your car will run fine without a tune but ideally you would richen the fueling slightly in the mid to WOT range. Use the Hotwire from the EB on the 70mm MAF housing. You can also use the AU injectors if you have them because, contrary to popular opinion they are not 24lb/hr
If you do find some detonation creeping in, go back to the EB 55mm MAF until you have some tuning device(I use Moates 1/4 horse). You can also go someway to improving the situation by using an adjustable fuel reg and bumping the pressure a smidge.