gauges

[merlin3]

on my 72 c10 with a 509 merlin i purchased a new factory style gauge cluster.i have tried 3 new different sending units for the temp.gauge finally i found one that worked but after 30 seconds with it running the gauge is almost pegged and when shut off it stays there and the temp on motor is 115.the oil pressure gauge gets pegged all the way over and out of sight and that too stays at about 3/4 when off i tried a new oil pressure gauge today and had the same problem.any help is appreciated.i tried another oil pressure gauge and it read 60.