I have not read this game thoroughly and can not provide much information other than an informal impression. Basic combat with an alright character creation system. I mainly purchased this product to aid me in an old Twilight 2000 game back in the late 80's
Here is an abbreviated table of contents (The Morrow Project GB-1, 3rd edition)
The War (Background) pg. 1
Morrow Project Personnel (Character Creation) pg. 7
Available Equipment and Weapons pg. 12
Basic Loads (Combat System) pg. 32
Conditions in a Post-War World (Setting) pg. 45
Miscellaneous Tables pg. 62
Expansions ~
Personal and Vehicular Basic Loads and The Morrow Project Role Playing Expansion (GA-2)
This has been renamed - Vehicular Basic Loads & Hand-to-Hand Combat System. A 5 page rules supplement with 30+ pages concerning equipment.
Liberation at Riverton (R-001) Inside cover is the playing map with a 43 page adventure including more equipment.
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I've recently seen
The Road which may assist you in world building. The book (of the same name) can help with more details I would imagine.