It's important that the slip yoke doesn't bottom out at any point in the entire range of suspension travel. If it does, it will eventually hammer your pinion bearings, u-joints, and possibly transmission, causing damage. Assuming you do NOT have enough travel for it to do that, the easiest remedy in your case would probably be get blocks that have a slightly offset pin so they move the axle back a little. That should give you what you need. It's also possible to drill another hole in the perches, but that doesn't work well on short stock perches because they can "rock" on the springs. It's more of an option for aftermarket ones that are longer.