Starting issue that doesn't make sense..

[sector_ut]

Okay guys I am a long time fan of the site, and have used the board for guidance for a long time. (However, I am just now getting around to becoming a member!)
Here is the issue, and I really need some help on this one.
I have a 69 GMC 1500 SWB that I recently swapped out the engine (rebuilt 68 327 with HEI.) and the electrical (Painless wiring kit.) The solenoid was recently replaced on the starter, the battery has been checked out and is okay at 650 amps, and the alternator works just fine. (tested as well.)

So here is the problem, when I go to turn it over nothing happens, no clicking, nothing... (I do have power, lights, etc.. just nothing from the engine.) However, if I add my charger / jumper to the circuit it starts right up. (grounding on the battery post, not anywhere else on the chasis.)
The engine then runs fine with no problems. As soon as I kill it, the problem returns.
Any ideas on where to start, I am at a loss.

Thanks in advance for any help!

Brian-