I installed a heater core and the rig ran perfectly except for the heater core situation.....and now it won't even turn over. Tried charging batter, jumpin' it and it just won't go....could there be something I could of unplugged preventing this? thank you

Yip, check the computer connections under the glove box.

Reattach all the electrical connections and make sure they are all in right.

There is a blue black ended connector thing unplugged but can't find anything that it goes too......

Look harder, It has to plug into somewhere.