I have a 1992 z28 25th anniversary edition. I bought it off a co worker who has taken out the tpi 305 and built a 350 and put in it. The TPI wasn't enough to power the 350 so he changed it over to carburetor. It now has a Holley 650 2 barrel on it. Everything on the gauge cluster works. Temp, fuel, oil press, tach and speedo. They all work but the tach does not read correctly neither does the speedo. Is this a simple fix or do I need to buy a whole new cluster (Dakota digital is all I can find for $755). It does have the 700r4 in it. Thank you any help is appreciated.

 

350 bored 40 over, flat top Pistons, hydraulic roller cams, ported and polished heads, valve work with bigger springs.
700r4 with corvette servo, stage 2 shift kit, 2400 stall and 3.73 gears

 

There is a common failure of our tach that involves a resistor going bad and it is easily repairable by someone with electronic know how , if it is in fact that failure . A search of this site will turn up threads about it .

And if it came with other than 3.73 , that's likely why your speedometer doesn't read right . If this is the case , the gears for the VSS will likely need to be changed . Again , there are threads to be found here dealing with ratio changes and how to get the right gears for the right ratio .