Current rims ok for 35-36's?

[hAetWagon]

I've got a set of 31's on my Blazer that desperately need replacing.
After doing the lift and whatnot on the truck it looks like a toy going down the road with rollerskate wheels on it.
My Question:
I currently have 15x10.5s for wheels on it. The track looks narrow.
When I go to 35's-36's am I going to need to replace the rims with ones that have less backspacing to allow for the tread?
or are my current rims going to be ok?
I'd love to hear "no" as i can order the damn tires and not have to worry about the Extra 520.00 for wheels.
But the truth will suffice too.