Gauge types & interchangeability

[Brad_Olson]

My '77 C10 has a fitting and tube for oil pressure while my '78 C10 has a sending unit. Does this mean that '73-77 oil pressure gauges are mechanical and '78-87 gauges are electrical?

Does anyone know if all '78-87 clusters are interchangeable? I'd like to replace my '86's cluster or at the very least the speedometer.

At a swap meet yesterday I found 2 clusters with the factory tach and vacuum gauge - $70 and $100. Unfortunately they also have ammeters instead of voltmeters so they won't work in my '78 or my '86.

Brad