" So how does the 8D compare to the T-105? Well the water capcity is about the same per cell, so is the lead content. Just the 8D is in one reall REALLY difficult to lift package. Lifespan might be the same, just I don't want to lift it."
This is like saying a Big Mac is Prime Rib because it contains beef.
The THICKNESS of the plates makes the GC batteries a totally different proposition. 500 CCA versus 1,100, far fewer reserve minutes. But a lot better survivability and number of cycles under heavy use. Positive plate thickness is an element not to be overlooked. A few months ago I posted a link to a battery company in the northwest USA whom listed all the specs for their 8-D's and they appeared to be cyclable.
But a 29 plate 8-D is NOT intended to be a cyclable battery despite weighing as much as a pair of GC220 batteries, acid capacity being the same, etc.
When tar-top 8-D's went the way of the dinosaur, so did the thick plates and high antimonial content. There are a few cyclable 8-D's out there but the price per amp hour versus the GC's is cruel.