Thanks for the advice!
There are two ROM's marked 390629-02 ROM0V5 / 390630-02 ROM1V5 in U180/U181, I guess the 3.1 ROM's goes in here, right? There are also two empty slots marked U182/U183 with labels ROM0/ROM1, any ideas what these are for?
Would there be any issues with the A3640 in A3000, or does it plug right in?