[Spridgets] cooling system issues

[ryan.kubanoff at comcast.net]

Reviving a 74 midgit. I last posted about leaking antifreeze from the radiator cap of my expansion tank after a ride. I replaced the cap with a 13 Lbs cap and today after a 27 mile 50 minute ride  to and from work i had antifreeze coming out of the overflow tube on the expansion tank. I also have a broken temp gauge to make things more interesting. I checked the overflow when things cooled down and it is half full but the radiator is down about 4".  What is causing this?  My plan is to replace the thermostat and the badly corroded looking crossflow pipe on the bottom of the radiator. is there anything else i am missing or should try while i am at it?  There does seem to be a small oozing of oil from the head gasket but not enough to reduce oil pressure or volume.
any ideas?
thanks
ryan