My 1999 GMC Suburban K2500 6.5L diesel was really hard to start this winter, and a frayed block heater cable didn't help any. After replacing the block heater cable and dropping in the two new batteries from TSC everything is working MUCH better.
I put in two of these bad boys:
Weight: 41lbs ea
Previously I had two Energizer batteries the previous owner purchased at Walmart. Never again!