Oh, Gordon. You're such a kidder!
Those packs are leftover Academy parts from an M10 kit. The straps are nice, thin lead foil from the dentist ("hazardous waste" from bite wing X-rays -- sterilized in an autoclave).
I think the tracks are also Academy (though they may be AFV Club ...

) I may replace them with RHPS before the AMPS Midwest Regional in October. The rubber blocks on the front are leftover RHPS tracks from my M12.
I'll get some close-ups of the .50 and other details when this bad boy is done. I still have lots of paint and weathering to do. I'm debating about leaving the pioneer tools body color or doing them in bare wood and steel. Have to look at the pics again.
Rick -- I'm tempted by the M4A1 direct vision, but I think the M4A1 with applique (maybe do Battling B---h or Derby, like Gunnie) or maybe the M4A2 will be next. I already have a M4A1 DV in the collection I converted from a Nichimo kit (ahrghhh!).

Jeff -- The mix-n-match tracks are kind of an Italian theater thing I noticed in photos. I've seen 3-bar-cleat armor on rubber-chevron shoed Sherms, rubber-block on rubber-chevron, rubber block on 3-bar-cleat, etc. When they raced across Sicily, they must have worn out plenty of tracks and decided to use them to increase frontal armor -- and almost always in the same place. There might have been some kind of field-mod order?
Lots of good, inexpensive references that show these tanks. I've been using Squadron's old "Sherman in Action," as well as Concord's "The M4 Sherman at War" as my primary references. For details on this tank, including the old .50 cal. with the small ammo can, you can't beat Squadron's "M4 Sherman Walk Around." I have Hunnicutt and some other Sherman refs, but haven't really needed them for this build.
Gunnie -- Thanks for the support!
Get moving with Derby! I want to see your take on the bizarre rack on the rear of the turret.
Keep the questions and comments coming, fellow Shermaniacs and Shermaholics!!