Just finished a build. tripple checked all connections and cables, verified no leaks. went to crank it up, and as soon as i put the key into accessory mode the starter starts grinding ?

 

Sounds like two problems, first is that the starter is not aligned properly. Second is you defiantly have a wiring problem. I don't know how much you tore down the wiring, but I would get a Digital multi-meter out and a wiring diagram and diagnose a few things. Check your grounds as well.

 

What he ^ said I don't know how extensive your build was but something is not wired right. The ignition triggers the starter solenoid to engage and the starter arm to spin, and shouldn't be doing anything if you're not actually cranking it.

Could also be something with a starter or ignition relay being jacked up but that is highly unlikely considering you just did a build and now all of the sudden you have the issues.
Check all the wiring in the areas where any work was done, specifically check the starter ground and wiring to make sure they are in the correct spots.

 

Figured it out, it was a wiring issue.