is it possible to run a 305-70-16 on an 8 inch wheel? or would a 10 inch wheel be better?

 

Here's a 305/70 on a 10" wheel, which you can see is perfect. I personally consider 9" the minimum and an 8" too small. Your sidewalls will be extremely bowed in on that narrow of a wheel which will increase sidewall flex and affect handling. Nothing dangerous by any means but maybe something noticeable...plus, it'll look like crap. Personal opinion of course. I wouldn't do it, but is is physically possible?? Yes.

 

I run them on an 8" wheel. The sidewall bulges more than the pics above but not bad and looks better and tougher than a tire that’s closer to the wheels actual width. With regular rotation and proper inflation I'm getting perfect wear and no handling issues. Plus if you ever take your truck off road having the narrower rim means you can run a lower pressure safer as the wheel holds the bead to the rim more.

 

Running mine on a 10 inch wide and think it looks just right