I have a rusty 1990 3.0 4WD pickup that is a donor for my 1995 22RE 4WD pickup. Does anyone know if the cold start injector timer switch, front brake calipers, and radiator are interchangable?

 

Calipers and radiator should swap. On the cold start timer, see if the connectors are the same and then see if it will physically fit and then you could look up the time/temperature specs on the two parts in a Factory Service Manual and see if they are similar.