I really like your website, it is very interesting and some useful MF information there.I installed a Walvoil spool block in my 590, scroll down that page:
http://haapasalontila.fi/MF590hydraulics.html
That is with auxiliary pump and now there is one pressure hose from aux pump and other pressure hose from linkage pump through 3-way selector valve. If not aux pump, then there is only linkage pump available and you must choose with the selector valve if you use the rear lift or the spools.
More original style solution would be to use Kontak sectional valve board.