I was told it needs an obd1. Before I order it, is this what I need? I have a 1994 7.3 IDI uhaul van. Overdrive works, light just blinks non stop.

 

You don't need that. I am pretty sure I posted this in one of your other transmission threads:
Ford ? OBD/OBD2 Trouble Codes

 

Yeah, that's when I was trying to do it on my own. It's at the tranny shop now, the guy says he used to have the reader but he lost it and it's so old that he doesn't need one, until now. I was thinking of buying one. That link shows 7.3 turbo diesel. I can't find the 94 idi econoline

 

That reader will work on yours.