tire width

I am having my stock 1976 kz900 swingarm extended 6".I believe this will allow me to mount a 170 series tire.
Will this be possible to mount to a stock 16x3.00 mag wheel or will i have to change rims after the mod?

yeah your stock wheel is about right for a 130 tire;)

Here's the chart I have bookmarked for these kinds of questions:
tire and rim size crossreference
they recommend a 4.5" rim for a 170.

thx for the reply Bruce. im kinda new to the mod part of customizing a bike.i always ran all stock. this is the first sport bike i have owned in 22 years and wanna make it a head turner.