its not that hard
Is your truck a 3 speed or 4 speed now??--if its a three speed,a TH350 will bolt in place of it fairly easy,if you get the right tailshaft length the old driveshaft will likely work,if its a one peice driveshaft--you will have to find a way to shift it though,a "three on the tree" shifter can be modified to work,or you can swap in an automatic steering colum or floor shifter....you need a tranny cooler too,if your radiator doesnt have one(most manual tranny radiators wont,unless someone swapped a radiator from an automatic in)....A 9 inch tailshaft is the most common one used in 2wd trucks,but there are exceptions...
If you have a 4 speed,it might be more work,some of them used a two peice driveshaft with a carrier bearing ,you might be able to find a one peice driveshaft out of the truck you get the automatic tranny from--the tranny mount might be different,but they arent that costly--you might have to move the crossmember to different holes in the frame....
If you want a TH400,you will need to move the crossmember,change the driveshaft to a TH400 style(they have larger splines on the tailshaft than a TH350)or you can use a conversion U-joint to allow the TH400 yoke to fit a TH350 or standard tranny driveshaft,but the TH400 is different overall length than a TH350,so the shaft will need to be cut and altered to fit,unless you can score a truck with the whole setup intact,then you simply buy everything you think you might need(nothing beats having the whole truck next to yours when swapping things like this..)so all told,it can get involved--the TH350 would probably be easier to swap in than the TH400,but its not as strong,but they arent weak either...its up to you to decide if its worth it to you to convert...
It might be easier to just buy another truck thats already got an automatic tranny in it---or teach her how to drive a standard !!..
