Engine swap questions

Hi, I'm fairly new to the site. I'm sure this question has been asked many times before, but here goes. I want to put a fuel injected small block in my 70 Dart 2 door hardtop. I'm considering getting a 5.2 or 5.9 Magnum out of a late model truck as a good starting point so I'll have all the accessories, wiring,sheet metal, etc. I'll also be running a manual transmission...4 speed or possibly one of those aftermarket 5 speed trannys. I was wondering if I will have any problems with the PCM if I don't use the trans. that goes with those engines, or does the PCM even control the trans. on those vehicles. Is this a fairly straightforward swap or am I going to have major issues. Any help is greatly appreciated. Thanks.