Anybody Know Of An In-Tank Electric Fuel Pump...

I bought a 3/8" inlet with a 5/16" return sending unit from Vans Auto
http://www.vansauto.com/sending2.html

What PSI are you wanting?Carb or Fuel injection?
No reason why you could not cut the pickup tube and install common pump like for GM products or use this sending unit like it is a mount walbro on the frame rail...
Here is a good read on slan six.org:
http://www.slantsix.org/forum/viewtopic.php?t=27101&postdays=0&postorder=asc&start=0