1994 GMC v-6 to V-8 swap

[Loyd]

we are installing a 350 into my 1994 reg cab GMC work truck V-6/auto. and want to know what we need to do as far as the ecu. Do we have to change it out completely or can we have it reprogrammed. also how to handle the vin number. if a scan tool is pulled in with the real vin it will think it is testing a v-6 so do we change the vin as far as the ecu is concered to reflect a v-8. oh for the days when you could just change engines with just two wires and some fuel lines.
Thanks