I had a wood boiler given to me that has 2 -3/4" return and a 1- 1 1/2" output pipe. My question is my exsisting oil boiler has an 11/2" return an a 11/2 output that was bushed down to 1" can I leave the 1" or do I need to remove the pipe and bushing. I have been told that sometimes removing threaded pipes from a cast boiler can crack the boiler.