stripped out waterjacket plug...PMC

every year it gets harder and harder to deal with the brass plugs on my engine block. I have a 1980 454 PMC. I just tried to get everything back together for the first trip to the lake and found out that one of the water jacket plugs threads is so rusted out that when I tried to screw the plug in it stripped out. I know I need to run a tap and die through it....my question is do I go one size up and also what about the metal fillings? My buddy said they would be flushed out the back with the exhaust...Any advise and tips on this would be really helpful. Also when I winterize do I take the plugs out...drain and put the plugs back in? Or do I leave the plugs out after I drain the block (it seems like this leaves water pooled on the threads....which causes the rust. HELP! we are getting very close to boarding season!

Joe's link took me to the general selection page. These are the ones he's referring to:

Joe also mentioned you may not need to go to the next pipe size. This is true if the threads aren't that bad. Try running the same size pipe tap in first but just a little deeper than the factory did. Since pipe threads are tapered, this will make the tapped hole slightly larger while cutting new threads. The danger here is if you have to go too far to clean up the threads then the hole will be too large and the plug/stop cock won't tighten. If that's the case, then yes the next step is going to the next pipe size.

Your original plugs should be 1/4" pipe size.

I also agree with Joe on the chips.

A little anti-seize on the plug during re-installation goes a long ways for rust protection.