Oil to Gas - should I move to \"pumping away?\"

I am replacing the second generation oil boiler in a radiant floor heated home built in the late 40's. The new gas boiler is an RBI Spectrum 150 decomissioned from another location. The current configuration has the pump on the return side. The new installation in 1 1/2" copper would permit relocating the pump. Second: What temp would be recommended for heating water (floors are ceranic tile or flagstone on slab)? It is hard to determine what was used as the old boiler had already gone to it's reward. If I ran the boiler hotter and mixed return water for floor temp it would permit adding rads to an add-on room but this is not necessary.