G'day Oz,:-D I think a 904 swaps a good one to.
And yep a bit better converter will be a good thing while ya doin it.
Dominello are your closest I think then The Converter Shop or
Dominator and TCE are both in melbourne, shop around tho, converters are dear!
You could also get a shelf TCI or Coan from mancini, just price it up mate.
If your still running the Bog Warmer diff, you could just find an 80's pintara and get the 411 gears out of it?
But the pinion is longer in the 82 and up housings so dont install the collapsible spacer, just shim it.
Sounds like ya on the rite track tho, good luck.
