As for 6 speed cost, you need at a minimum:

- 6 speed box
- Auto front stub axles, unless your 6 speed is non DCCD from 02 and earlier, which means your shafts will drop straight in without having to change the stub axles
- Clutch fork
- Gearbox mount
- Tailshaft
- Shifter
- 3.9 rear CWP in your stock R160

You can use the 5 speed clutch and flywheel and starter motor so thats no problem.

I'd budget $5k ish supplied and installed.. thats assuming you pay between $3500 and $4000 for the box with most of the above parts supplied, plus install, oil and CWP supplied and installed.

You can probably do it cheaper if you source the box from Import Monster yourself, but I'd personally save the trouble, spend the few hundred extra and buy one thats already here.. at least you can inspect it.

Try the Classifieds for the bits you need, and hit up Doug @ STechnic for the install.