Problem is that's a chassisworks rear frame kit designed for a much higher frame to ground distance. ladderbar brackets are under the rails,and if rails are say 5inches of the ground then pivot point is going to be 3&half or less. they can be fixed by relocating a new set of brackets onto the crossmember,and new brackets on housing for about 200.00 total verses the cost of a 4-link. Plus if the shop thought that geometry was going to work I would not want them installing a 4-link. Not to mention that the kick up in the rails is going to be to far forward for the 4-link plates. So your talking more involved fab work thats going to look like an afterthought at best .IMO move the brackets inward till they are level with ground with one hole left up as well as down