Depends on how much spring lift you have to start with. If you're running stock springs, your forward movement (without the blocks) will be minimal (maybe .5 inch)
I just put the ORD flip kit on my '86 with 12" lift springs and it moved my axle forward 2". (Which is a LOT, BTW)
For the record, I love the ORD flip kit (and all their products, acutally) just know that if you start playing with the flip and blocks, you could experience a LOT of axle movement. And realize that as your axle moves forward, your pinion angle gets worse. Nothing that can't be fixed, but just something to think about.
Best of luck...