Speedometer background change

I was wondering if i gave my guage cluster a facelift and put in a 155 mph face to replace my 115 mph guage on my 2.73 equipped Z28, would i be able to just send my PCM into a place like PCMforless and get it re-tuned to read the correct speed on the 155 guages? Or am i going to have to buy a whole new guage cluster if i want to get rid of that speedo? Sorry if this is the wrong section, thank you in advance

You just need a used 155mph cluster out of a junk yard car. After that, its plug & play, no tuning.

Thanks Injuneer but the reason why i am asking this question, is this if for my 94 and i love to brag that its barley got 30k mi on it so i still wanna have my odometer read correct. Since i plan on getting a few things tuned on the PCM as it is i just figured hey maybe i can just put a biff background on, and have the speedo needle calibrated for a 155 mph background.

that should work find, essentially your changing the gauges.