Have completed a complete conversion on my sv6 wagon about 8 months ago it cost me around $2500 with doing the work myself that's also including getting my original ecu remapped as you can't use the ecu from the donor car
Did you have to do anything to the Firewall to get the clutch pedal through? you'd assume that Holden would be
total cheapskates and use the same bodies for Manual and Automatic cars instead of making two separate bodies for two separate transmissions. Someone's gotta do a writeup with pics for the conversion process at some point to determine how possible it actually is since nobody's actually documented it afaik.
For reference, As far as I'd know you'd more than likely just swap the box out, swap the wiring harness from Auto to Manual, Flash the ECM and install the hydraulics for the clutch pedal. Afaik the clutch and brakes share the same master cylinder reservoir in these cars? V6 and V8s share the same master cylinder part number but have different slave cylinders on the count of the gearboxes being made by different companies (V6 = Aisin, V8 = Tremec),
Please correct me if I'm wrong here btw.
Also if you do end up spending the time and money doing this OP, i'd highly recommend doing a SMF conversion on your clutch. Mantic, Exedy and Xtreme do organic HD clutches for the V6. I'd personally go with the Mantic if you've got the dough.
As for insurance and Engineering woes? I'd take it that this is where you'd run into the most trouble. Insurance companies
really don't like you doing mods so this is where your problems (and your money) is/are going to end up being.