Motorcycle Gear Indicator
Suzuki made many of their bikes back in the 80's with gear shift indicators. You might want to check out service manuals for the GS425's through the GS 1000's from that decade. Please don't ask how I know something about those machines. :lol:
As for your tachometer, there are a number of electronic project sites on the WWW that show PICs with multiplexed seven digit displays. This means that one data bus is used to provide data to all the seven segment displays, but individual chip select signals are used to coordinate which display is enabled at the same time that its data is available on the common bus. If you cycle the chip select and the display data fast enough, the human eye can not see the display flicker. Or, you could use a data latch with each seven segment display, and use the chip select control to update each data latch individually.