Got the right head on this morning, hooked everything up and it started
right up, at least from the sounds of the initial idle.
It is powerless, though, and it feels as though the throttle is connected to
the accelerator by a long, soft rubber band, meaning that there is a strong
lag behind pressing the accelerator and the rev of the engine.

The engine may (or may not) idle nicely for a while, and then the rpms fall
and the engine quits.

I know the spark plugs are going to the right place. Could I have the
injectors swapped? Could the new, unprimed lifters be doing it? My
experience with setting valves on cars tells me that it couldn't be this far
out by making a mistake in the valve timing, or could I be wrong about that?

Thanks,

Jim