I know the alcohol race cars have an additive that comes in many flavors, coconut, strawberry and febreeze,. Maybe you can get smell good for your gas.
I think it's the motor, I have a 307 2 barrel that I will swap you straight up that doesn't smell musty.
If I had a 427 small block I wouldnt' care how it smelled, I would know its BA, and cruise it as is. It smells musty because it's old, or maybe it's the mothballs used for octane boost causing the smell.