afaik the later model computers will run as is, but it's really a good idea to get the EVTMs and go through and correct any differences in the computer harness. on therangerstation.com, they have a 2.9L MAF conversion pin out showing differences between the later model and earlier model wiring that would be good to reference (minus the MAS wiring). The only thing you need to worry about is if the computer is for manual or automatic transmission. 86-87 would be safest, 88+ will allow you to remove the EGR system entirely. 88+ 2.9L Rangers did not have EGR systems.