Are you going with a Lexus lump, or something else? Thats the first thing to consider.
I'd expect the box/idler to be easier to accomodate than a rack.
Ls1 or similar.
Well, yes. It would be, as that's the original design.
...and yes it is just a rack. But for the sake of 3 inches width in the engine bay.
You'll note the title. "Fitting" a rack. There is no, "not Fitting" a rack. Lets have a more positive approach aye? 
Chill Pill

Some threads are "I want to use Castrol Oil/Falken tyres". Note, NOT "I dont want to use Castrol Oil/Falken tyres". The whole point of an interactive forum is to gain/share ideas, either wacky, inspirational or just plain sensible. Live with it.

I was the GM Omega V8 (not the omegav8.com) a rack or box. I thought it was the latter. I was thinking more along the lines of if GM have already done all the hard work, and pretty much proved it all worked well... ...but what would they know

Sorry if I misunderstood.