Coil choices for my truck?

Despite the one-step-forward two-steps-back progress I'm making, the new slant for the truck is almost done. I was going to replace the coil with an upgrade unit, but there were many choices and no clarity as to which one would be correct. Or maybe I'm over thinking this...

I'm looking for one to fit the stock location, about 40K volts or so. The engine is moderately built for a slant with a Super Six dizzy and HEI conversion already done. The confusing part is resistance of the coil, and how that is supposed to affect things. A bunch of internet digging hasn't helped clear this up any.

What say the experts?