The issues with the LML are that each year has a different Operating System, but they can have an unreal amount of combinations of other segments, the fuel segments especially for the Cab and Chassis are not the same as pickups.
Better hope you don't get a stripped down LML with a manual TC, no 4x4 would suck if it does not engage because you have the wrong system segments.
You can try to build them by swapping segments but many just are not available online anywhere, even though many are out already.
You also need a subscription to TIS for getting the stock files, that alone costs you $1000/yr on top of a $500 Mongoose Cable for getting the tunes flashed in.
Add in a TECH2/CANDI Module to properly log some of the LML parameters and your costs keep going up and up and up to do this properly.
And swapping OS from one year to another doesn't work well at all, some say it can be done but there are major differences in the code and the later ones have extras that the earlier ones do not.
Most of the problems are because of an incorrect base tune, and getting it read out requires a specialized fixture, boot pin, software and a hex editor that is compatible for import to EFI-Live for final editing.
The initial investment is keeping the market very small as only a handful of us have the proper hardware/software to offer this.