Do the turbo and non-turbo b230s use the same large tachometer?

Yep.

is there a different tach for the turbo and non-turbo cars?

Nope.

I'm looking into getting a large tach/small clock setup for the 1986 240 non-turbo.

Should be an easy install. When you go "shopping" at the boneyard, be SURE to get the small harness that connects from the back of the tach to the small clock.

Also, when you dig into the cluster assembly (that originally contains the tach), be sure to grab the small, black plastic thingy that fits into the hole (in the cluster plastic window) formerly occupied by the clock adjuster shaft.

This is also a good time to install a voltmeter in the lower accessory spot. I've done it to every one of my 240s over the years.

Store all the original parts away -- you can reinstall them in your '86 when it rusts away and you buy another 240 sans tach. I've moved one tach/clock kit through three 240s over the years...

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Don Foster (near Cape Cod, MA)