I've got a 4L MPFI EBII, and just recently, its been running at fairly high temperatures, for example, 110 down the highway on a 15 degree day, and its on mid-temp! then i have to watch out when i turn off the engine, as the radiator starts to bubble and the temp slowly rises. Now my bottom end seals are stuffed, sorta, and im getting a new engine rebuilt as we speak.

Now, could this sudden temp problem be caused by the worn engine? or would it still have to do with the cooling system?

More likely your radiator is full of s**t, and needs a good clean out or replacing.

mine bubbled when the head gasket was blown had to keep the cap half undone to keep it happy and cool

yeah i figured it would be the radiator... was just hoping it was more of an engine issue, as it will be resolved in a week and a half anyway with the new engine.

oh well, i spose i should prolly give the cooling system a once-over anyway since a new donk is being installed

Yes well worth a new radiator, give the new engine the best chance you can.