2001 explorer sport Trac wont Start and change battery, starter, and relays

hey guys,
I need some ideas because I am all out of them. let me give you the low down on my truck. I just swap a 4.0 v6 2003 ranger motor into my truck. when I was replacing my battery because it was bad i accidentally put the terminal on back on wrong way. spark shot off and i heard click from the fuses box. so I pull the negative off. I put them on the right way and the truck started no problem. I drove into around 5 times then it wouldn't start so I smacked with a hammer started right up. I figure it might have to do the the starter relay because they rapidly clicked when I hooked up the battery the wrong way. so I replaced the relays along with pcm relay and all the fuses Still no luck. So I took out the starter and had tested it was dead. So i replaced the starter it still wont start. I check the wire that acts like a fuses it was fine and i clean the Iacv (what ever it name is) when did the motor swap. the battery read 12.34 on my multimeter. any Ideas guys?
thanks tom

update

and it 12.34 to the terminal on the fuses box. i hear click in the cab but not under the hood from the relay or starter.