I did that with both my bikes (think I'd learn eh) I tried a few combinations and picked the least tight one put the pump together and both have worked fine since despite being tight to turn by hand.
I could be wrong but I suspect the manufacturer of these piumps ( did BSA make them or buy them) would not have spent a lot of time matching gears to gears to pump body, probably just built up spun round to bed in until they were free, flushed through and used.
I would not worry about fitting a pump that was tight to turn by hand, it will be running in oil, will bed in just fine ( much maligned soft metal body remember) and provided you change the oil soon after fitting (as you do) it'l be good.
Now shoot me down fella's, I like to buck the trend now and then