The "wizards" can stick to chevs and small blocks.
Have found an engine builder thanks to Ozze427 and spent several minutes talking to them about my situation.
The "MAN" instead of trying to sell me a Windsor or Cleveland told me to expect 700hp and 600 torque, figures they have met on several FE Builds in the past.
"No replacement for displacement" were his exact words!!
It maybe FE Fantasy at the moment but it's a whole lot better than the Frustration I've been experiencing.

Take a bunch of pictures of your gear and if you want I will post them here
for the brain trust to comment on.

my addy 390fairlane@gmail.com

I'll try put them up otherwise ill email to you
Thanks

How loose? I've got a feeling 7 sounds right.
It never blew smoke but it did ping (rattle) a bit when pushed hard. I thought it was a loose exhaust bolt or timing?
The bloke says they're forged pistons and they've got fomoco stamped underneath. Valves have hit and scored 2 pistons slightly but I wouldn't know what I'm looking at.
They're all the same shape and not burnt or melted in any way? Rings all look the sme and the bores look brand new. When I first went there he said the pistons were ok, the next they're shot?

Thanks for the quick response fellas.
I've measured it roughly when I stripped it down and it went 4.233 so I thought I'd won the lotto as in it still was original bore size.
The blocks getting sonic checked somewhere else as these guys haven't given me a print out and I doubt they've even checked it.
As to it being an irrigation block, I don't know, it has the steel crank $ stamped, the factory machined chambered heads and fomoco forged pistons, lemans rods with cap screws and ford sidewinder intake.
So from my understanding all the gear that points towards a normal 427. Does have the ribs cast in the block though.
The shop also told me the pistons were very undersized.
The only other experience I've had with big blocks is in a couple of 428 mustangs (weird when you think about it as fe's are rare here)
My Fairlane was a completely different animal to these stangs and the engine was much meaner quicker and louder than either of the 428's.
So surely I haven't got the only 427 block ever poured that's too thin to rebuild?
I'll get proper results and post so the experts can help.
Barry I'm guessing you can supply pistons any size?  I should've known I do have yours and jays books.
Todd I'll pm my number to you again.
Thanks guys and I'll be back with some figures soon.

Apologies Jay,
I'll remove and repost with price.
I'll pm those interested.

Why not make it the lower 49 and include Western Australia???
I'm sure Todd wouldn't mind

Ross mate, I'm not even going to embarrass myself with a reply.
I pulled and stripped the engine undoing bolts and nuts is about my limit and I'm not real flash at that

Beautiful Mustang by the way

You can't blame me for getting excited and wanting a 8000 rpm 800hp monster but this is why I joined this forum.
Ross, you are right, I'm used to small blocks and being underwhelmed by them  so I'm probably shooting a bit high with this engine. 
Bud has summed it up pretty well perfectly with regards to what I want from the car/engine with the only problem being the block isn't drilled for oil to the lifters ( as far as I'm aware).Hence the reason I'm leaning towards a solid cam.
 Other things like oil holes have been chamfered and ramped etc on the main bearings and where the oil filter mounts. When I had the exhaust fixed at a local shop that specialises in old style cars, very few FE though, the bloke said it had an aftermarket cam but I don't think he'd ever seen or heard a 427 before.
The iron heads I had new springs,chrome moly retainers, the ports blended and valve seat grind.
According to Luigi the Head man the heads had already had bigger Manley valves and hardened valve seats for unleaded?  I had this done after blowing a head gasket and blew a second one a month later hence the rebuild.
So I think the block has been prepped before and the little mods I've read about eg the oil holes chamfered etc have been done which  makes me think Bud is right and to spend the money on the heads and valve train.
The car has Holman Moody stickers on the windows but most fairlanes probably do.

I've been in contact with Blair Patrick and I'll leave it in his hands to come up with a combination that works, although he is already breaking my heart by trying to convince me a RPM would suit better  than a Victor.
Victors "look meaner" though.