Weld a metal tab (washer maybe?) to the sump in the middle of the dent, pull it out and grind it off - bingo!

Click to see on Trademe
Probably not suitable as a daily commuter?

I went to a motorbike wreckers and bought a doodad that fits on the end of a single cable and enables you to join two cables on to it. So you end up with a "Y shaped" cable - single at the knob end and double at the carbie(s). I seem to recall paying about $25 for the doodad and two shortish cables that came out the carbie end. You can use a standard datsun single cable inside the cabin and it will look right.

I'm going with nickmitty - dragchute

That looks like a lot of fun and RH drive!

PM'd re gear knob

At least a grand

Should've posted a comment to show appreciation. I found it very interesting also. I kept going back to see if you would show us how to put it all back together properly.

I can volunteer another box if that's what's needed

Is it registered in Vic? Where are you in Melbourne?

63A box - ticks all the boxes! Hard to find but worth the effort as it's all a bolt in fix. Should be strong enough to cope with a turbo (and these are the key words for any transmission) if used with some care.