There is not a single word that does a good job filling either of those blanks. As fumblefingers said, the closest you will probably get is "over" as in
There is an excess of A over B.
But this really does not sound natural. I would recommend you use two or three words; specifically, "relative to" and "with regard to" or "in regard to" work well here:
We have an excess of A relative to B
There is an excess of A with regard to B
Another option is to rearange the sentence a little:
We have A in excess of B
All of these work well for this situation and are precise. In this case, your ratio is 1:1, so it would actually be easier and just as accurate to simply say one is greater than the other:
We have more A than B.
While not correct in a formal manner, this technique would still be a good way to say that you had too much A for B even if the ratio were not 1:1 in many contexts, as the ratio is implied.