Tire size on 74 Z1

I am getting ready to get my Z1 out for the summer, it needs a new front tire. I am liking the look of the Metzler ME880, I am wondering what is the widest tire I can run on it? Bike is stock in terms of rims and swingarm and such. Looks like there is a little room on the front...and not much in the rear. Is the stock setup just the best way to go on this?
Thanks.

Have you tried the "Search Forum" function. Been covered loads of times.

Later, Doug