Imprezas have 3 main harnesses, the engine harness, the dash harness, and the interior harness. Again, I'm no expert, but usually with a swap, you only change out the engine harness. If you change out the dash harness, you may need to also change out your '94 dash to a '97+ dash, and then your doors might not close like one friend of mine who did this with a '95 L that got a Ver 6 swap that included the dash. So then he had to source Ver 6 door moldings to make it all fit. It turned into a massive headache for him. Another guy I know did a '94 WRX motor swap into his '97 Impreza, and his dash was considerably different from the '94, yet that '94 motor had previously been in a '93-96 style US Impreza.
So just be prepared for headaches. The less things you change over, the better.
Oh, and yes, the cluster will fit physically, so if you're not afraid of wiring, you can probably make it work.