AR-5, r-154 Anybody actually done this

AR-5 is the Aisin designation, GM called it the MA5 and you can get them out of Sky/Solstice roadster's too. Definitely a cheaper option than the R154, but it's only rated for 260 ft-lbs of torque. Some info as well as vehicles they came in Aisin AR transmission - Wikipedia

The R154 I think is by far the most desirable option for this route, best ratios, strongest, most aftermarket for replacing parts or beefing it up further. The AR-5 would be next. I wouldn't even mess with an AX15, it's a truck transmission and more work than it's worth in fabrication. An 833 OD can handle more power, and they aren't all that much more expensive (I've bought a couple for $200), and have better ratios even if the spread is larger. And they bolt straight in.

I was considering this swap myself, but those were the issues that caused me to make the decision to go straight to a T56 (after saving more money). The 340 in my Duster is good for ~400 hp if not a bit more. The r154 would work, but by the time I found one and built it the cost would be pretty significant. The AR-5 probably wouldn't live. And if I have to convert to a hydraulic clutch and fabricate a crossmember already the additional fab work for a T56 isn't that bad. More expensive for sure, bellhousing costs a ton, transmission costs a ton, plus all the extras. But with a t56 magnum being good for 700 ft lbs I don't ever have to worry about engine upgrades. Plus, better first gear ratio (2.66 vs 3.75 for the AR-5 and 3.25 for the R154) and an extra gear! You can go 3.91's or 4.10's no problem and still cruise easy. Heck I got the .63 6th, with the .5 version you could go 4.56's.