I've been in touch with Redline, but they will only modify the stock amp gauge to a volt gauge if I send them the whole instrument cluster for them to make the mods. That just doesn't work for me, as it will be far too expensive for me to ship the cluster from Australia to the US and back again.
Is there any other place that sells a volt gauge that is ready to be installed into the ebody rallye cluster and that then looks almost stock in appearance? I'd like something that has same backplate, needle, colours and fonts as the original amp gauge. I know it's not going to be 100% original, but I want it to look like it's meant to be there.
Other than that, It's looking like I will just have to buy the Sunpro volt gauge, replace the backplate with my stock amp gauge backplate, replace the needle with my stock amu gauge needle and stick that it the cluster. Hopefully it won't look like a frankenstein assortment of bits in the end, but maybe I have no other choice.