Most reputable OEMS will provide you with a barrel type pump with nozzles and flanges to suit your requirements. Large multistage barrel pumps for the likes of boiler feed, water injection etc are of the 'engineered' variety that is to say not mass produced so can be custom made including the hydraulics.
While it is technically possible to engineer a side-side BB5, the issue of adequate supports is not a trivial thing. I am sure it can be done but I personally have never seen a request for one.
I have designed BB5 pumps with 45 deg suction nozzles (and one time a bottom suction nozzle) for power station boiler feed.
OTOH I've done plenty of side-side BB2 pumps so why not try a BB5 ?
Point taken Pumponly & Bradshsi re side nozzles. By side nozzles I didn't necessarily mean at 9 & 3 o'clock. We were supplied 3off replacement 11.5 mW units for installation recently with delivery nozzles set at 45 deg to the horizontal to match original pipework geometry.