CarlB, sorry it took so long to respond. I was out of town last week at meeting.
I bought this battery tray on ebay.
Boat Battery Tray with Hold Down Strap for Standard 29 and 31 Series Batteries. The tray dimensions are (Overall inside dimensions) 13" L x 7-1/8" W x 1" H
The bracket I had made measures 14 x 9 x 12. We used angle iron for the tray support & uprights and a piece of flat bar for bracket strength.
I drilled (4) 5/16 inch holes in the frame and bolted the bracket to the frame using lock nuts on the bolts.
Ive attached some pictures that should help. If you need additional assistance feel free to pm me. Good Luck!
PS: Don't laugh at my drawing please!!!!
Kettrell & Sharon