Claymore - I have the AFV workable suspension here and was just looking at it. It is the mid production suspension without the upswept return roller arms arms. A real quick glance through my reference pics and all I see are the upswept variety that come with the Tamiya kit. Of course when it comes to Shermans, that doesn't mean much all the time.
As far as detail sets go, there are a few PE sets that can be used. Royal, Aber, and Eduard all make sets for the M4A3. What I usually do now is just get the Eduard zoom sets that are only the brush guards. I've found that I'm tossing too much of the full sets in the parts box.
Interiors for the M4A3 hull are available from Commanders Series Models, but a little scratchbuilding willl give you much the same thing. Nothing that I can find for the 105 turret.
Another option (at least for the hull) would be to use the interior parts from the Academy M10 series kits or even from the Italeri Priest / Kangaroo kits. These would give you the basics under the driver's and co-driver's hatches withough huge expense. A little detail under the hatches and you're on a roll.
Commanders site - http://www.commanderseries.com/armor.htm
Royal is available at - http://www.chesapeakemodels.com/
Happy Modelling and God Bless
Robert