It does move pretty rapid with engine speed. I'm not sure if you could use the original gauge because I would assume that the sender/gauge combo would need to be a match set.

I only had an idiot light to begin with, and found out the hard way that the light will only work if the wire is hooked up to the sender <img src="/forums/images/graemlins/shiner.gif" alt="" />.

An engine rebuild later, I vowed to have a real gauge. <img src="/forums/images/graemlins/kewl.gif" alt="" />

'06 Dakota QC 4.7 6sp 4x4
'88 Mighty Max
'77 KZ1000 fun old bike