You can remove the wire from the low limit side of the aquastat which will keep the oiler from maintaining temperature however that old boiler is at least 50 years old and closer to 70 and it was assembled with push nipples so there is a good chance it will leak when it goes cold. The best thing you could do with it is send it to the scrap yard. A new boiler will save you a good 20% on your heating bill and probably closer to 40% Those old Arco's were pigs. The flue passages are big enough to toss a cat through. Does it still have the original Arco burner hung on it?