Water Leak 300E interior

I am trying to find a water leak in my 91 300E. Car has 124K and is in nice shape, but sat outside in a yard for 2 years. The front floor mat is out, and rear seat has been out to de-mouse the car. I have noted standing water in the recesses of front and rear floor, intermittently. I have checked the sunroof drains and they seem intact. I have had a friend run a hose around windshield and rear window, without finding a source. I suspect it is front WS. There is no evidence of prior removal or body damage to the surrounds.
Any advice would be appreciated.
My current next thought is just going to windshield shop and remove and re-seal front, then same with rear window if not successful.