Tire widths

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Hi all , I have been lurking on the forum for a while but this is my first post. I have 15x6 and 15x7 fuchs replicas, my bug is a 76 standard with ghia discs up front and dropped spindles, back spacing on the wheels are 5 inches.It is time for tires and I want to make sure I get what fits! I would like to run 50 series on all 4 or 55s up front with 50s in the back .Any advice is appreciated. I would like to keep the front fenders stock,as for the rears I could go with glass. How wide can I go?