E85 compatible 5.3

[summitXMK]

I was reading the article form the home page of gm-trucks.com about how all 2002 5.3 liters will be e85 compatible. Does anybody have any more information about this? I was wondering if you have to order it this way or if they will are just have the abillity to burn both. Also how would I find out where I can buy this stuff.  Just to make things even more complicated would it be possible to rebuild a 1976 400 smal block motor to burn 100% ethanol or the E85 ethanol.