Why new wheels with a lift kit?

[HGW]

What do you mean they willnot know if the wheels will work until the lift kit is on?

Go to another shop.

It depends on the lift kit you use---some have new spindels and these new spindels could require a certain backspacing. A simple read of the lift kit instuctions could tell you the backspacing required.

If your shop cannot tell you what your backspacing is, then go elsewhere.