Classic/Antique Car Repair: Muffler on 63 Ford Falcon, 63 ford falcon, glass pack

Question
I am replacing the gas tank, the new one is a little larger than the original, the new one makes contact with the muffler, I am thinking of replacing the muffler with one of smaller diameter, any problem with this idea? or can I just shorten the exhaust pipe and move the muffler back where it clears the new gas tank?  The engine is a 6 in line 170ci. Thanks for the advise.

Answer
There is no law that says that you cannot reposition the muffler to make room. I would rather see that than using a smaller muffler that may or may  not change the exhaust flow pattern that the engineer designed into your system. However if you want to make it sound like a tiger with a nice mellow exhaust growl then a glass pack or similar muffler would work but it will raise the cabin noise as well.
Brad