Agreed. Before you tear it down and measure/inspect journals and such, you have no way of knowing whether the block is still original or if it has been previously rebuilt and already has oversize bearings/pistons/etc. There are service limits that come into play, if it has been oversized to a certain point, it may not even be rebuild-able.
If you have never done it before, either read a lot, or let a machine shop do the measuring.
