I have a 1998 ford Explorer Eddie Bauer V6. I need a transmission. How do I tell if it's a OHV or SOHC?

and what is interchangeable with it?

if you look under the hood there is usualy a plastic cover on the engine that would tell you, best to call a autowrecker with the vin to see what you have and what it interchanges with

If you have a 98 then the V6 was a pushrod type engine. Check the engine code on the vin against a site on the net. If memory serves the pushrod engine has engine code X, but not definite.