I've got some of the resin Tank Workshop conversions for the USMC M4A2.

Tamiya's Red Army kit is not one that you want to start with; it's turret isn't correct for a PTO vehicle. It's more than a simple barrel swap out for the 75 mm turret and the 76 mm turret.

Using the older Tamiya 75 mm (35122) or the 2002 retool (35250) is a better starting point if you wish to begin with a Tamiya kit. Of course, half the kit is vintage 1977 and the kit has been bypassed by much better versions.

Here is a good kit that will get you to where you want to be, and is probably cheaper than the Tamiya kit even before the conversions you'd need.

https://www.scalemates.com/kits/dragon-6462-m4a2--106235

Another starting point is the venerable Italeri M4A2 that also suffers from age as well. While the turret is from the mid 90s, the base kit goes back to the 70s with the upper hull from the late 80s.

https://www.scalemates.com/kits/italeri-6389-m4-sherman--133516

Dragon M4A2 "Tarawa" kit. The wading gear is from Tank Workshop. The rail is Evergreen styrene. The applique armor is sheet plastic.

The venerable Tamiya M4A3.  

Wood side armor is plastic sheet. Sandbags are epoxy putty. Wading gear is scratchbuilt from sheet. Mesh screens are leftover Eduard PE or scratchbuilt. 

This one's a total mutt. It's a Verlinden M4A2 upper hull and turret on a Tamiya lower hull. Dragon bogies and wheels as well as some other small details. Wading gear and wood armor is all plastic sheet. The water tank is built from a piece of an old pen of suitable diameter. Tracks are from Bronco. 

Googling images will give you a good idea as to how the modifications evolved during the campaigns. It will also give you the progression of Sherman variants used. 

The kit in the link, the late M4A2 would be good for Saipan, Pelelieu or Guam. They werent used on Iwo Jima or Okinawa despite what all the experts say. The M4A2 early was however, used on Iwo Jima by the 3rd Tank Battalion. 

Ohhhhhhh those look cool guys!

Tim: I hope you'll post her when you're done.