Hi Ron S,
You might already know what worked for me, installing two 6V AGM batteries where I once had 12V wet acid batteries in a slide-out tray.
CLICK HERE for pictures and write-up. I removed the 12V battery slide out tray, mounted a flat steel plate to the battery compartment frame, and framed the batteries with angle-steel. Doing so increases the working height to set the batteries in a conventional upright position. Given they are maintenance-free, there is no need to fuss until replacing them. I later marked "+" and "-" on the batteries to know which terminal was which at a glance.
If your battery compartment is exposed to the rear tires like ours were, the opportunity presents itself to close-up the battery compartment, a project I did many years earlier.
CLICK HERE to see pics of that project.
Ron Dittmer