Trouble with starter

So I bought a starter that's from a 92 Dakota and hooked it all up to my 74 duster and when I turn key over I'm getting nothing. I have a 73 column (auto on the floor) and it is now 4 speed I hooked the starter up like normAl but nothing . I already know it's not my ignition switch because when I turn key my light on my msd box comes on. Not battery cause radio works maybe I have something wrong have pos. Battery cable to starter than smaller cable to positive on the relAy then negative to relay and then to neg. On starter. Why in the world isn't the starter turning over .. ????