1999 chevy express 1500 4.3, tires on as of now are 225/75/15. The tires I would like to purchase are 235/75/15, will this work? I am buying a heavier load range to handle the weight in the van!

 

Sure. They are slightly taller, so you will have a longer drive ratio. you will be going a bit faster than the speedo says, and so on.....buts its not a big difference.

 

The size should be fine. But realize the heavier load range will not allow you to carry a heavier load... at least not over the GVW.

 

You can still carry your max gvw. It just means that the tranny will work a bit harder with the longer gear range to get going, and the shift points may be a bit off as well.
His difference is 2% larger and well within the max 3% that is recommended.
The 235's will only turn 15 less revs per mile.....