Im putting my coilovers that were in the back of my cj into the front of my xj I have a 300 lb 250lb and an 80 lb coil. The 80 over the 300 gives me the ride height I want but is it a problem to run rates that are so far apart? I was thinking once the 80 bottoms out this would give me 300lb rate so if I going fast I would have some botttom out resistance.

thats a light rate for the front. set the slider stop ring low so the slider bottoms out an inch or two before the shock does. this will transfer you from the combined rate of the two springs (63.15 lb/inch) to the 300lb lower. You'll still bottom out but it wont be as often or as harsh.