1991 Dodge "power" Ram pickup

I have a faulty speed sensor - speedo odo and abs are out to lunch, I get the dreaded #42 speed sensor message on the check engine light. Speedo starts working, accurately, after about 30 miles of driving.

Now I ordered one on line for a 91 and got something that looks suitable for a bicycle - basically a reed switch with 8 poles per revolution. The one on my truck appears to be a "variable reluctance" type (basically a coil of wire around a magnet - gives a pulse out every time a piece of ferrous metal (gear tooth) passes by the probe).

I searched and searched but the one that is supposedly for my truck doesn't even begin to fit (physically - even if it was the right type) and the pictures for the one that is in there look like they belong to the 1996 Dodge Ram.

Is there anyone out there who can 'splain this, and which is the right part? Likewise - I haven't measured the ohms of the one in there, but what should it be? Anyone wound or repaired one of these? ) I'm an Electrical Engineer, not an auto mechanic.

Ah yess, "Built Ram Tough," Good thing too - if rams were built "Dodge Tough," well, they'd be extinct now wouldn't they?.