what oil should i use in a rebuilt 5 speed t3 transporter box ?

Go by Exactly what the owners or service manual says, at least for the first fill. We have heard of recent failures of rebuilt trans's with some "mainstream" oils, even though some or all of the spec's seem to match. Try to find a true major-mainstream supplier, I.E. Mobil, Caltex, Shell, or BP(='Castrol'). Then you know product should be 'right'. (Avoid any others.) Their spec's may include more recent version no's/dates of the original ones. (Some of what may appear to be VW spec's are actually their product-approval doc's., which may be less important than they seem, though this may be a more recent thing.)

ok so oil for the gearbox anyone got some actual suggestions based on current information not outdated service manuals made 25 years ago ?

To choose a Castrol oil:

http://www.datateck.com.au/lube/castr_au/ 

To choose a Valvoline oil:

http://www.datateck.com.au/lube/valv_auMS/ 

Use a GL4 not a GL5 oil.