What year is my Auburn chassis?

Thanks Andy,
Found the frame # exactly where you described.

frame numbers are stamped on passenger side aft of the rear spring hanger. they are stamped VERY LIGHTLY!
do not get in a hurry trying to find them using a grinding or sanding disc.
There are a few posts here that have photos that can help to guide you in your quest.
I do not think that your frame was originally red though....

I have a '31 or '32 8-98 or 8-100 chassis (127" wheelbase). The engine number is GU 70554. Can someone help me with the date of manufacture or model year? Is there a chassis number stamped somewhere on the frame? The frame was originally painted red. Does that mean anything?