Sorry for the lack of details. The label on the original water heater is torn and I can't read the manufacurer's name, and the rest is completely unreadable. It is a much older model with a cardboard case with fiberglass insulation between the cardboard and the tank.
Here is a photo of the original heater:
The new tank is a Suburban SW6DWE 6 gallon and is the same dimensions. I was already able to test fit it in the original location and it is a direct fit. The water fittings on the back also align. The location of where the gas supply line is run along the side of the heater is the same. The difference is that the connection on the new heater is male instead of female like the old one and the new one is at a 45 degree angle instead of 90 degrees like the old one.
Here is what the new one looks like:
I found a video on Youtube showing them replacing an older model just like mine with a newer Suburban model and they reference that you will need to swap the older style gas supply line with a newer one, but they don't say anything about where to get one or if you need to make one. The installer simply states "I have already changed the gas supply line".