My mate as a EF (maybe a EL) block.

We want to mess around with an AU crank. We were thinking of putting a Au crank in this motor and rebuilding it. So new everything for the bastard. We will also install a cam into this as well.
We were thinking about a AU head but we wernt sure about this.

Just wanting to know about anything in putting different motor components into a EF motor??

Au has different diameter main journals. You would be up for additional machining costs to get it turned down to EF/L size but it is possible.

I'm currently building an EF block with AU rods. I prefer the EF crank. The AU crank is no bad thing though!

If you want my opinion, unless you plan to build a monster race engine, just get a low-kay AU motor, convert as necessary and be done with it.

You get the crank you want, plus longer rods and a main cap girdle. Stick whatever head/cam package on that on you've got a healthy performer without the fuss.

We have a EF/EL motor already but we wanted to mess around with an AU crank.

I also hear the BA E-gas cars have Typhoon con rods because of when the gas back fires on a normal car it can throw a rod, so the e-gas motors got the phoon rods cause they were stronger.

the EF rods are stronger.

just rebuild the EF engine with ACL race series pistons and bearings, that'll be plenty strong enough for anything with a sane rev limmit.
the smaller dish in the piston will mean less milling of the head the get the compression up and that in turn will help with piston/valve clearance.
you'd be looking for around 10.5:1 compresion.