'61 6 volt starting issues

I bought this car about 2 years ago and have completed, almost :-), a total body-off restoration. Literally every part, nut bolt and washer has been removed, perfected and replaced. Wiring is brand new and the vehicle started..intermittantly. Let me give specs - Original 40 HP 1200 motor, original 6v tranny, the starter is a "new" napa rebuild with an orignal Bosch rebuilt genny. After the ignition circuit was wired, the vehicle cranked and fired. It was a tear jerker...lemme tell ya! :-) However, I was having major generator issues with the Napa genny I bought initially. It was cooked out of the box. It never charged. anyway..... the issue I have is I can't get it to crank more than once. I know that sounds lame... It isn't a bad battery... I bought 3 new 6v batteries and they all can't be bad. After trying to crank the motor once, then once again, etc... I felt the batt cables and they were warmin up. I thought maybe an amp flow issue? Bad connectors somewhere? Bad starter?? I don't want to convert to 12v, and I know all about the Ford solenoid trick, but I want to keep it 100% original... Has anyone encountered a 6v system that simply didn't want to crank? When it get's lucky, it cranks 3 times or so and will start... but it is soooo hit and miss (like 1 out of 50 tries), I am freaking out! :-) Any ideas will be appreciated.
Looks at the bug: http://home.comcast.net/~joshandsony1/vw/vw.html

What about the starter bushing, was it replaced. Try connecting a wire to the solenoid directly & see how it cranks.

The transmission was rebuilt and a new bushing was installed. When the starter is tested off the car without a load, it engages and spins. when installed, with the flywheel load, it boggs down and will not crank... You think it's just another cooked starter?

Can you put an ammeter on it? That would be the most definitive test.

Unfortunately, I don't have an ammeter. Something else just came to my attention on this starter, however.. I just removed the starter to replace it - upon reinstallation, I was going to replace the starter bushing in the bell housing. Looks like when the tranny was rebuilt, a bushing was either not installed, or it was vaporized somehow. Could a bushing failure cause a no start situation like mine?

Yes, a worn or missing bushing will cause the armature to rub on the windings. Sometimes the can still turn slowly, but usally draw too many amps and quit.