Well i guess some of the japanese engineers did R&D on this whole pumps vs engine sizes. And i guess theres a reason that a 760cc is pushing a 155mm pump in a WB2. I really don't think its fair to say "any motor under 1000cc will be fine with a 148" same as saying anything under 850cc will be fine with 38 mikunis.
Why not get most efficiency out of the gear you got?
As for the 155 OEM setup, you can find pretty good deals on complete drive trains, thats what i did. Only thing to be aware of, is that you need a custom drivesahft +15mm. If you use your SJ 96-07 OEM driveshaft, the spline engagement will be 15mm less of what its supposed to.