How do I locate a good center line?

[Alaskan]

I am compiling a pretty thorough list of steps and to-do's for when my truck arrives next month, and one of my first things to do is mark a good center line down the middle of the frame (and body?). While it sounds pretty straightforward (pun absolutely intended), I am wondering from which points I measure from on the frame to find a center? Is there any magic sauce to it, or should I just measure from the left and right suspension mounts, find the middle, and run a laser down the frame? Is there any reason to match up the center lines on the body too? There doesn't seem to be much wiggle room on the cab to chassis mounting for the truck kit from what I can see, but it wouldn't hurt to make some reference marks before I take the cab off. Thanks!

[NAZ]

For a longitudinal center line I used the suspension mounting points attached to the chassis to measure from. I've used lasers where it's difficult to use a string line but prefer the string method as most lasers project too wide a light. I'll place permanent witness marks in strategic locations on the chassis where they can easily be picked up after the car is assembled, which most often seems to be on a bottom side. I'll drill a small hole ~ .070" if it will not compromise structural integrity but never drill into tubing. If not drilling i use a prominent center punch mark.

You also need a datum line marked perpendicular to the center line. I typically use a rear bulkhead frame rail or the rail that the LCAs mount to on a solid rear axle. I measure to ensure I have witness marks perpendicular to the center line even if the tubing or chassis member I'm marking them on is not. If you make your witness marks a cardinal and equal distance from the center line it will help later as these will be known distances when you pick them up later. For instance, placing witness marks 20" from the center line on both sides makes it easier when measuring from that datum to a projected line depicting the track as an example. No need to reach all the way to the center most point to measure from.

[rponfick]

Recommend doing this early, not after you are at go-cart stage. I am attempting front alignment and wish I had measured a good center line before now.
Good luck.
Ralph