Do freeze plugs work as they should???

:sad1: When I bought my Dart, it came with a 360, the block was dated 1978. At least a couple of the freeze plugs were missing. The car ran well, but with no coolant, it was only permitted for very short periods. The previous owner states it had water in engine and was left outside overnight, causing it to freeze and subsequently pop the freeze plugs. Like I say, the engine runs well, but I have since pulled the engine, initially planning to install a 383, am now considering keeping the 360. Does it have to be stripped and subjected to various methods for locating cracks at a machine shop, or should I put new freeze plugs in and pressure test the coolant system and go from there. Just don't want to waste time on a cracked block.