i am 100% agreeing with you, keep them Original!!
I agree also!!!!!!! Plus they circulate the diesel engine oil and warm the cooling system before the diesel is started. I have a 66 D7E ,original owner, with pony that has around 19,000 hrs and only had the starting engine rebuilt ONCE! it still runs perfect! I always let it idle and warm up after starting it and idle back down then turn gas off to stop it. Take care of em! And change the oil in them often!