I seen today at work on a sheet that comes with the rebuilt chevy alternators that they have a wire for the signal for a tach. What type of tach would use this?

6.5s for 1 use alt for dash tach signal, PCM triggers off of the crank sensor, this is why correct Alt pulley is critical when you replace, I suspect other autos could alos use this tach reference for speed display.

No sig info, Odee - what truck are you wanting a tach in?

I'm thinking about rebuilding a 6.5 for my 80 model dually that I haul my jeep and drag cars with. Also rebuilding a pair of late 60's four wheel drives one for my friend the other for my son's 16th birth day, we have given thought to putting a diesel in one or both of these trucks. I was just curious when I seen on the instructions about a tach signal coming out of the alternator. Any kind of tach work with this or is it gonna have to be a spec type tach?

The late '90's tachs use one phase of the alternator output, requires specific-to-Diesel pulley diameter.

Is available a combination vac pump\tach\oil pump drive assy , also a tach\oil pump drive assy from 6.2\6.5, can be used with the original V8 tach from the '60's-'70's-'80's gasser trucks.

Electric tach drive is a black plastic module on top of either assy, was used for emissions computer, and auto trans control.

Are there small tachs that would attach on the top of the steering column? My '93 came without a tach.

Also, would the mechanically injected 6.5s run the tach from the alternator? Or the oil pump? Thanks.

tach drive normally would run off the oil pump drive. I'm not sure what would be involved in adding a tach drive to a vehicle that didn't come with one, but I'm sure its possible. I don't know if you could hook it up to just any tach with that system or not, might only work with the factory one.

6.5 tachs are alternator driven.

Most of those V8 tachs from JCWHITNEY and such will function off the oil pump drive tach sender, with a few simple parts from Radshak

BTW - you might scour the local boneyards and get the optional instrument cluster with the factory tach.
Should be simple swap-out, adding the tach wire out to the alt post.