No such model exists.
You need the services of a CNC machinist.
You will need to call Colt.
You need to contact Colt
7.62x25 is the Tokarev pistol cartridge. No manufacturer currently makes an upper for that cartridge.
Try AR15.com Try AR15.com
If it is one of the recent Colt .22LR AR15 rifles, then the answer is no - they are completely different internally.
1959
Yes
The US Army presently uses the M4 carbine, a shorter and much modified version of the Armalite AR15.
Colt has not offered a AR15 in 308
why would anyone need to know