[Chase_K]

I would do what Curran suggested, I just cut out as well but holy shit it gets loud and fast in here quick.

 

[Hodgdon Extreme]

My r154 setup used OEM is300 trans crossmember, with some ~1.5'' thick spacers between crossmember and chassis. I did'nt have any vibrations.

Careful choosing a clutch. Puck style clutches will all chatter.

 

[IS300 2001]

So upon further research it looks like there are 2 types of AR5 (MA5 really) in the colorados/canyons and hummers. It depends on whether it is 4x4 or 4x2. We want the 4x2 version. That looks to mount up like the solstice/sky AR5.
What I have been able to find, and kind of just deductively say this, that 2004-2012 Colorados as long as they are 4x2 trucks and not V8, they use the same transmission.
I say that because when I looked up the part number for the manual trans for a 2005, found this:

2004-2012 GM Transmission Assembly-Man 24284716 | GMPartsDirect.com

2004-2012 GM part # 24284716 - Transmission Assembly-Man

www.gmpartsdirect.com

This says this transmission fits a 2004-12 Colorado and Canyon. I assume that any year in there with the 1jz bell housing, with the 5mm shim I posted above, and the custom shifter, should work in the IS.
I plan on trying to go to get that transmission at my local yard tomorrow morning, if its not pouring rain. I'll let you know what I find. I believe its a 2005 truck 4x2 that it is from, from what I can find on car-part.com

Did you ever end up going farther with this project?? I'm very interested as there are no Solstice AR5s nearby, yet plenty of Colorado ones.

 

[Hodgdon Extreme]

The Polaris slingshot also uses an Aisin-built R154 variant. Don't know details, but I know an R154 when I see one. Might be worth looking into.