Welcome to the board and congrats on your "new" truck.
If the "stuff" from the tank has come loose, you really need to drain the tank and remove it from the truck for a proper cleaning and sealing. It isn't that difficult of a project. I used the POR-15 process on my '53 3100 tank and was very pleased with the results.
You should really take the carb off too, for a proper cleaning. These carbs are very simple to work on, You most likely have years of varnish and crud built up inside the carb diminishing it's performance. A kit wouldn't hurt either. Removing the carb is a straitforward job, takes about 5 minutes.
Your carb is most likely the dreaded Rochester model "B". You could also have a Carter YF model which was a popular aftermarket carb.
Hope this helps,
Steve
