Could anyone point me in the right direction on what are the physical differences between Army Abrams MBTs and Marine Abrams MBT's. I am looking for either a list or photos or links . Thanks JDM

Army and USMC use the same M1A1HC (heavy common, known in modeling world as heavy armor). The only always present difference between them is that USMC use different type of smoke grenade launchers.
Most USMC tanks have the bustle rack extension added, but some Army units also started to use USMC type rack extensions recently (earlier only 3ID used their own rack extension, different from USMC ones).
Many USMC tanks, but not all, have troop phone in a box attached to the rear of the hull.
USMC use "dazzler" - Missile Countermeasure Device attached to the manhole cover on the turret, but this is additional accessory and can be removed (although usually mounting brackets remain on the turret of USMC tanks even if MCD is not installed).
All USMC tanks have a flange for mounting the deep fording kit on the exhaust, but many Army tanks also have this part.
And finally USMC tanks sometimes have the track retainer rick attached to drive sprockets - part which Army stopped using many years ago.

Pawel

Current or Desert Storm M1A1s? During Desert Storm, the Marines borrowed early issue M1A1s straight from Army stocks stationed in Europe. Those were identical to Army ones except for the tactical markings.

The Marines have added their own flavor to their M1A1 heavies. Many items are easy to identify like the missile countermeasure device (MCD) located forward of the loader's hatch on the manhole cover. Although to the uninformed, this has been mistaken for the CITV of the M1A2.

The other easy identifier is the use of the four-tubed smoke grenade launchers (they use a pair per side-8 tubes per side/16 tubes total). The Army uses the standard triangular shaped smoke grenade lauchers.

Just what I needed. Thanks for the speedy response. God I love this site.