Your other option is to fit an Ashcroft factory reconditioned LT85 from the UK,
Ashcroft Transmissions - Santana LT85 this will cost you £550.00 (aprox au$910) plus shipping. There is a depost of £225 (A$370) for the return of your exchange unit, however with the cost of shipping you may as well pay the core charge and forget the exchange.
You will still fit it up to your current LT230, but there is no added cost of all the conversions and trying to find an Isuzu/LT95 bell housing.
It will last you at least as long as your current LT85 without all the headache.