old brake master cylinder/reservoir

Hi folks, I have a couple of old front brake systems sitting around for my track bike and I'm thinking of fitting one of them back on to replace the brembo setup I have now, it appears the bore in the brembo may be wrong giving all the braking preasure in the last little bit of lever preasure and almost no feel before that.
One system is completely dry, the other still has some very black looking fluid in it, is there anything to beware of before transplanting either onto the trackie, given that it can't really be tested prior to first use at the track?
Matt
One system is completely dry, the other still has some very black looking fluid in it, is there anything to beware of before transplanting either onto the trackie, given that it can't really be tested prior to first use at the track?
Matt