We have this 12 bolt it has the following numbers on it could someone tell me what they mean 3969341nf gm63 con2 2345 67880 b50 the rear is 45.25 from the center of spring perch to spring perch and the distance to backing plates is 55 inches

I found this right here in this forum......

3969341NF could be late '69 Camaro or '70 Nova or '70 Camaro. If it's a late 69 Camaro or 70 Nova, it is a bolt-in. 70+ Camaro axles need the perches moved to fit in a First Gen. Camaro.
Check out these threads....

http://www.camaros.net/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=6;t=003269

http://www.camaros.net/forum/ultimatebb.php?ubb=get_topic;f=6;t=003324#000000

http://www.camaros.net/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=6;t=003266

http://www.camaros.net/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=6;t=002368

http://www.camaros.net/forum/ultimatebb.php?ubb=get_topic;f=7;t=005789#000000