Stuart, Are you arms like these:
These arms need the axleshafts of the same car.
What length axle shafts have you got? Are you using the 1303 axles or the longer ones from the same car as the ali arms?
Is your intention to use in this order:
Porsche hub
Porsche arm
Porsche hub flange/stub-axle
Porsche CV joint
Porsche axleshaft
T1 CV joint
T1 output flange
If the splines are not exactly the same profile, they don't fit and may break under abuse.
If your Porsche axleshafts are the same length as the 1303 axleshaft you can do:
Porsche hub
Porsche arm
Porsche hub flange/stub-axle
T2 CV joint (needs clearancing for T1 circlip)
T1 axleshaft
T1 CV joint
T1 output flange
T181 output flanges are the holy grail of this conversion and it would be a doddle, Porsche strength everything!
Do you have a digi camera? That would be a great help to get help.
Matt