Good luck on tracking the problem. The BATTERY CASE is the place to find the TERMINAL markings on the batteries. Sometime just having pictures of the old install may lead you astray on hooking them up. You can the markings on the battery case to make sure you have the cables going to the right places... Sometimes the CASE MARKINGs are different even with the same brands of batteries but newer manufacturing dates.
Having a mulitmeter in the RV tool box is a great idea. I got two or three layin around here somewhere from my travels.
The crowns are the top of the line batteries and you sure don't want to hurt them before you even get to use them...
ALot of folks like to hook two groups of 6VDC batteries like this is their battery boxes... This would be my choice if my battery box allowed me to sit the batteries in this layout orientation.
This is the 6V battery setup for dual groups you mostly get to see which uses longer lengths of cabling...