FWIW - when I bought my '78 40, I was NOT able to set toe-in correctly with the original tie and relay rods - they were NOT threaded deep enough. The FSM says 'set toe-in at 1/4"' - I only needed an additional 1/8" of toe-in to stop my 40 from drifting all over the road, but had to replace the tie and relay rod to accomplish that additional 1/8" - when I replaced them, I also replaced the TREs and RREs.
I learned that the rods were not threaded deep enough when I discussed this with cruiserdan - he's the guy who told me that they were 'bottoming out'.
Since the FSM says 1/4" and it obviously worked for years, I
assume the fact that I needed an additional 1/8" was the result of my 40
possibly having slightly larger tires (30x9.50R15) than stock - or the fact that a PO installed a mix of mini-=truck and FJ60 power steering or something along that line.
I don't really know, all I know is my 40 stays completely true since I made this change.
Also, as someone touched on above, if you are going to replace tie/relay rods and TREs and RREs, if you buy them from cruiserdan or beno, you will get 25% off, but you will need to buy two TREs and two RREs, each TRE and RRE will come with its own rod (you can't buy the rods from Toyota - you have to buy the Ends to get the rods) - not sure why they are sold this way, but the price is good and it leaves you with a spare tie rod and a spare relay rod... should you somehow need them.
I don't know what year you have, but IMHO, if you are replacing TREs and RREs, you should really replace the rods to ensure you have latitude to properly set toe-in.
Also, using suggestions by a number of MUDders, I was able to break my rods loose from the Ends by exercising 3 days of patience, a lot of heat, simultaneous taps from two hammers on opposing sides, penetrating oil,
remove the collars and drive a large screwdriver or cold chisel into the slot on the each end of the rods - to 'spread' them - assuming you are replacing the rods! Spreading the slot worked really well, but damages the old rods.
Also, if you are NOT replacing the Ends, be careful you don't melt the boots on the Ends.
HTH