93 caravan electrical problem

here is my problem the van was working fine until I busted a radiator hose and kept driving with it, so guess what? I warpted the head and head gasket,insted of reparing it I decided it would be easyer to change the hole motor witch I did, now the real problem is that when I start the van it won't stop even after puting the ignition key to off position and also to make things worst the alternator won't charge unless the key is in the off position, cause when I leave the key on, I drain the battery and all the accessery star to flicker on and off non stop.
now I thon't know what my problem could be but it's driving me nut's

this motor came from a 1992 grand caravan
ps: I tried changing the hole wirering under the hood,the tranny,the pcm (power control modual), tcm (transmision control modual)that came from the same van as the motor but no luck