I found this thread:

https://www.clublexus.com/forums/ls-...-base-rwd.html

However, it's referring to the ISF wheels on a base LS460 base rwd. I'm assuming the bolt pattern is probably the same between the LS460 and LS600hL, which from what was posted in that thread would mean the 600 will need adapters for the 2008 ISF wheels.

But beyond this should the 2008 ISF 19's fit the LS600hL? Where it was a RWD car, does that mean the ISF wheels staggered widths - and would this be a problem on the LS600hL which is AWD?

I really don't like the idea of bolt pattern adapters personally, but yes, you would need them. Width of the wheels/tires is not what you need to worry about with AWD, the outer circumference of all 4 corners needs to be the same though.

LS runs 14x1.5 for a reason...

And that. Using adapters to go a bigger pattern is one thing, using them to go to a smaller pattern is something entirely different and is not recommended.

Patterns are what 5x114 ISF, versus 5x120 LS600hL?

Yes

.....

I found these, anyone hear of them before?

http://www.performancewheeladapters....-12x1-5-studs/

You won't notice the weight difference on a 4600lb car,my brotha.