What things to check for when looking a used Rotary over to tell if the engine has been previously overheated? thanks, for the help!!

 

If the water seals have failed, its a safe bet its been overheated.

 

sniff the upper part of the oil stick, if there's a burnt smell to it, then its more than likely it already been overheated a few times.

 

check for "leaking" coolant at the pressurecaps the stock caps are not exactly any good at holding the high pressure of boiling water.
It usually shows as green or blue corrosion on the aluminium waterhousing neck

 

If it still runs it is hard to tell if it's overheated before.

The common symptons are..(usually related to almost dead engines)

White smoke from exhaust
Lots of bubbles coming from coolant with radiator cap off looking at flowing coolant.

Coolant overflow into and sometimes out of resevoir.If they haven't cleaned the engine bay you can usually see stains from the coolant dripping out.