Another distributor question

[Dave Brown <davebrown1@earthlink.net>]

I am in the need of the list's expert advice once again.

I have two vastly different distributors, both supposedly from '79 1500
midgets.
One, Lucas 45DE4 >0176has a big box on the side where the vacuum
diaphram is, and has a three wire hookup.
The other, Lucas 45DM4 >3780 has no big box before the diaphram and has
a two wire hookup.

Does the number after the arrow give the mfg date?
What is the difference between 2 & 3 wire? external vs internal
resistor?
Is one better than the other?

All comments appreciated.

Thanks.

Dave