cast iron three pass boiler

We are looking for a three pass, cast iron,steam boiler,oil fired for burning waste oil.We currently have a American Standard Red Flash # 2 coal boiler which is about 85 years old or so it has a banna size hole in one of the castings that we have been jb weld glueing for the past 10 yrs.which is ok,however internals have much restricted arteries and steam productions has been poor this year.We are looking for a easy to clean steam cast iron boiler 500,000 btu's or so.We do not which to convert to hot water as the upper part of the systems is in perfect working order.Your help would be appreticated. Sincerely Len