First Post. Need quick advice

[80Sierra3500]

As my user name implies, I've got an 80 GMC 1 Ton Dually. 454 4BBL Qjet. Sometime earlier in its life, someone rebuilt the engine with an "RV Cam", a mild intake manifold (Edlebrock?).
I have been planning on doing the 4L80E swap for 10 years or so. Started looking around and found one that comes with an OBD2 setup directly from a 1998 motor home. Just read This thread on the LS swap concerning legalities and read several threads on the 4L80E swap.

My question is this: Will this setup have more or less horsepower/torque than my present manifold/cam produces on my otherwise stock 454? I've heard some of the injected engines can be lethargic.
Thanks Tons.