1969 chevy c10 short bed with 4/6 drop question

[tony989192]

first thanks for letting me join the site.

I've got a 1969 c10 short bed that I'm putting a 4/6 drop on and I was wondering how wide of a tire/wheel and what backspacing I could run. I've got a tubbed stepside bed on it. I know there's a few with this question but I couldn't find one about a stepside bed. I've also read about moving the rear inward and was wondering how to go about doing this to run a wider tire.

thanks for any help I can get