For the record, General MacArthur probably never had a Packard all during WWII. His cars (one for him, one for his wife) were Cadillacs and had license plates that were numbered USA 1 and USA 2 respectively. Mac LIKED Cadillacs. And historian and fellow SAH member Darwin Lumley and I many years ago went to check on the ship the supposed "MacArthur Packard" was said to have been brought back to the USA we discovered that this ship was in fact sunk off of Luzon many years before it was supposed to arrive in the States! While there were several military WWII Packards done up in what military people refer to as "O.D." (olive drab), it is highly doubtful that any of them belonged to General MacArthur.
Frankly, the best place to find war-restricted paint and chrome treatments for 1942 is in UA War Board and military specs for these vehicles. There are organizations that serve such collectors and through these one can can locate the proper publications that show precise requirements and treatments.