[Henry Schmidt]

Those would work but not nearly as well as a gradual transition with a 1" spacer.
If you make the spacers out of aluminum you can open them up when you get around to porting the heads. This plan allows you to get whatever benefit a longer runner might offer you. Depending on cam timing, the distance between the intake valve and throttle butterfly can effect engine performance.
Also keep in mind that "there is nothing more permanent than a temporary solution."