Years ago there was a discussion about the E-series V10. I THINK there was a tachometer output from the PCM, but finding it is a chore. I think there's one of those "blunt cut" wires under the dash for it.

Finding a tach that's capable of 10 cylinders, that's even more fun

 

Don't know if this helps. But it looks like Autometer has built an adapter for their tachs and the V-10. You might call or email them.

Auto Meter

 

More here on FTE, given my google search of "e450 cto tach" (where cto stands for clean tach output, learned from the autometer page linked to by David).

https://www.ford-trucks.com/forums/1...10-engine.html

Looks like you should be able to find a white/pink wire labeled "CTO" under your hood

Also this thread:

https://www.ford-trucks.com/forums/2...achometer.html

 

Yes I found the cto wire stubbed out under the hood..I called autometer about their tachometers and they said I needed one with 5 pulses and they want an arm and leg for one of their's..I guess that I will do without..

 

Found this, but still, $110 for a tach?

Summit Racing SUM-G2969 - Summit Racing® Pro Series Tachometers - Overview - SummitRacing.com

 

I found one on ebay for $39 and ask the seller if it would work on a v-10 and he they said it would if I could fine the tach wire which I have found..It's a Sunpro cp 7908 from Summit racing...What do you all think about it? I don't want to buy it and it not work and have to send it back..Has anyone tryed this tach? Thanks

 

Owner's manual for that model only shows 4-6-8. Ask him to take a picture of the back of the tach

http://www.sunpro.com/publish/2007/0...lish_16475.pdf

 

The only Sunpro tachs I see that work with 10 cylinders are the "retro" versions.

SST802R and FZ88R

 

Weird though, Amazon says the CP7915 will work with 10 cylinder engines, but the Sunpro website doesn't say it at all.

I'd still say "look at the back and see if it has a setting for 10".

 

You could get a ScanGauge or the Edge monitor, both will show RPM and will add other functionality as well (mpg, temps, etc).