Here's a gauge overlay that closely matches the original font. You could probably email the seller and see if he makes that gauge with the correct green font. Shouldn't be a problem at all.
http://www.ebay.com/itm/Premium-Dash...f7d98d&vxp=mtr
Is there any way you could do a step-by-step on how you did this mod? I have been doing a lot of research on using an older Sun tach and modifying it to fit, but like you, I wanted a more realistic RPM range.