Is aliminiun fuel line legal for rego ? also for return line for EFI

I think you'll find Queensland Transport regulations allow you to fit unmodified replacement fuel lines. Which means replacing steel bundy tube with aluminium would not be allowed without getting it engineered.
As John said above, aluminium is not the best thing to use as it work hardens with vibration and develops fatigue cracks if not really well supported, is more susceptible to abrasion and damage under the car, and it will gall on steel flare fittings creating an imperfect seal.

David,

This link may help, most state authorities reference it:

http://www.infrastructur.../bulletin/vsb_ncop.aspx

here is the relevant clause from the section LM, Fuel Systems.

"4 BASIC MODIFICATIONS NOT REQUIRING CERTIFICATION
The following modifications may be carried out provided they do not affect compliance with the
ADRs, compliance with regulations including applicable vehicle standards and provided they
meet the following general safety requirements.
4.1 FUEL LINES
The fitting of alternative or replacement fuel lines may be performed without certification,
provided that:
�h the installation is in accordance with good engineering practice;
�h all components used are unmodified;
�h the fuel lines are secured, properly supported and shielded against heat, abrasion and
impact damage; and
�h the fuel lines do not leak."

I think your aluminium extrusion would not meet the requirement to be unmodified.