what is the size of my rim?

[BillyBlaze]

my rims are all rusted out, I am trying to figure out the size to order some new ones. It seems that every site I use for my other vehicles does not have an option for my truck on their site
I have a 73 cheyenne super 10 looks like 15in 5bolt rims are whats on there.
so would it be 5x100,x7?
also I would like to know how wide and tall I can go with a 15 inch rim.
I would like taller and a little wider with the rubber.

Thanks