Just finished a second careful reading of Feinstein's Intolerable Act, and it does appear to me that although the M1A is not specifically named, it is an "assault weapon" via the threads for the castle nut.
Here's why -
"The term ‘threaded barrel’ means a feature or characteristic that is designed in such a manner to allow for the attachment of a device such as a firearm silencer or a flash suppressor."
Since that bill only uses "one feature", we're burned if it passes, since the threads "allow for the attachment of a...flash suppressor" via the castle nut/FSB assembly. Looks like we get to keep 'em legally, but any transfers get kinda sticky - and possibly $$. There is a section towards the end that lets the BATFE set fees for transfers at their whim.
So any M1A guys out there who thought you were off the hook and sitting this one out - nope - please write!
All the best,