hi!
first of all.. you get a much better recording with capacitor-mics. they react much better to your source and produce cleaner transients. for recording this organ you should use mics from neumann, schoeps, or so... i suggest lending a pair or two of cardeoids. try the A/B - stereoarrangement and place the mics at the same height as the organ's positive... good luck!
(well, sorry 'bout my bad english.. i'm austrian)

greets tom