[dsraven]

just beware that any crossmember you install, if the truck is going to sit lower than stock, the axle center line may need to change otherwise the wheel looks to be too far back in the opening. it is best to have a wheel and tire the size you want to run when done, for mock up purposes. when doing the conversion place the truck on stands at the rake angle you want and also level side to side. a digital level is good for this but they can be pricey for a long one. what I have done is use the digital torpedo level sitting on top of my regular 4ft bubble level. a digital torpedo level is not gonna break the bank and will give the same reading no matter wht angle you look at it. a bubble level is really only accurate if read from straight on.
the factory assembly manual is a free download from the trifive site. it will have the frame and body drawings to show the factory axle centerline. most of the aftermarket cross memberts will have you measuring off the center of the front spring forward mount hole so a center punch mark at that location will likely help you later when locating the cross member. what I do is use a combination square from the clean frame to mark the fore and aft edge of the hole in the frame or the spring pin bushing hole. then find the center between those marks, punch a mark on the frame at that spot and use that as a standard reference mark. do both sides. most will say to move the axle center line ahead an inch or more, depending on how much your new suspension will drop the truck and also the size of tire you will run. larger diameter tire will show the difference more than a small diameter tire.
I highly recommend to read up on the independent front suspension geometry before you start so you know how what you are doing will affect the new steering characteristics of the truck. one reason why a bolt in unit may be better because the upper and lower control arm pivots are usually already placed in the correct spot compared to some weld in units where you will need to place those and hopefully get the dimensions and angles correct for anti dive and control arm angles and pivot point spacing