i've been concerned about this myself, in the state of MN. my AA is nowhere near completion (and in my mind, never will be... {rat}), but i'm concerned about it and would like some peace of mind. i have a bill of sale from the guy i bought it from, but i have found the year to be incorrect, the engine number to be from an A and not an AA, and haven't found a frame number as of yet. i'd like it to be registered as an AA, but without a frame number or an AA engine (or loose AA title), i'm not sure how i can do this.
i'm mostly concerned about cost-effectiveness. ease is a close second.