I have a couple of clevelands and they all have FMX with them, I have heard alot people say that they weren't that good of a transmission but the FMX's held up good with mine for a stock build.We had one that was in a 1956 F-100 but we took it out and now have a 460 in it,like what you are thinking about doing.If it is a 4-bolt main I would get it but that is just my opinion.Dave