Help - Lost Electrical Power to Circuits

Yesterday I installed my freshly rebuilt 440 in my old charger. As we were trying to get it started, after I cranked on the engine a few times I lost power to pretty much everything. There is power to the starter relay and when the ingition switch is turned on there is power on the out side of the starter relay. However, the engine does not turn over. Also, there is no longer power to the aux circuits like lights and horns and there appears to be no power to the fuse panel under the dash. Any idea what may have happened. Note, I had one of those trigger switches hooked between the battery and starter relay so I could find top dead center but don't see how that could have been the cause of the problem since the switch was not being pressed at the time we were actually trying to start the engine.
Thanks,

Sounds like either the fusible link or the bulkhead connector bad. The largest wire going through the bulkhead should be hot at all times. It feeds the whole system inside. You also might want to check the amp meter connections.

What Stump said, pull the bulkhead start checking continuities & if it is the FL find/fix the high draw/dead short that fried it

Do you think having the start switch tied to the circuit while trying to crank the engine could have fried it?

Shouldn't have. But leaning on the wiring while messing with getting it started could have broken the fusablelink or pulled on the bulkhead connector. The main feed wire connection could have been iffy and putting the strain of continually trying to start a new engine might have done it in.

Thanks. I will start troubleshooting and report back on what I find or dont find.

As others have said I bet its either in the bulkhead, or the ammeter is failed. Either one is very common, and easy to locate just take a light and poke around till you find where you lose power somewhere...

It ended up being a bad ground connection between the engine and the battery. I am not sure how it work for a few minutes and then stop but everything seems good now.