Found one!
Having just shelled out $1000 on a trip I'm taking this summer, I didn't want to spend another $150 on a tach, so I patiently watched ebay and I am now the proud owner of a 6v 6cyl tachometer.
[is stoked]
The best thing is that I'll have a helper next week and that'll be right about the time that it'll get here!
Thanks again for everyone's help!