I know this isn't really what you are going to want to hear.. but here it goes..
IF IT WAS ME
I'd sell that 18k mile bigblock and 4l80e complete for 35-4000.oo
then get a g.m. crate 96-02 350 vortec 350 and drop it in..
the g.m. engine all new is 2000.00 and will be plug and play..
that 454 drivetrain will not..
and depending on your laws in your area.. the swap most likely requires ALL THE EMMISSION equipment the 454 truck had.. ..
I know you didn't want to hear it..
but if you're hell bent on installing the 454 I'd go look at a truck with one in it. and take note of the wires and where they go..