[Oldsguy]

Dale, that is a beautiful car and the engine bay has been well detailed and looks to be well maintained. I guess you can sense our bias against non-Olds drive train swaps into Oldsmobiles. Sorry, it is hard to overcome those natural tendancies. I agree that if the seller really wants to move the car and has the knowledge they would fix those small items for you. Many mid to late sixties B bodies (like your 88) had a cable to the driver's front wheel which drove the speedometer, not sure about 1960 models though. This would be a positive for you as it would be easier to get the speedo hooked up than if it were driven off a gear in the transmission. We have some members that may be able to fill us in on that fact. As for the other gauges, if the oil gauge is of the direct mechanical type, not a problem. For coolant temperature, you could either get an original sender to drive the gauge and mount it on the chevy engine (wherever that would be), or get an aftermarket gauge with a sender, mount the sender and place the gauge in the stead of the original. This second solution would require getting under/behind the dash and could be difficult. Is there any kind of gauge for electrical system? Gen light, or a gauge or what? This may be difficult too. All these would not be impossible to overcome but just items to consider.
We can appreciate the fact that you are in kiwi land and US made car parts, especially for these older Oldsmobile may be hard to come by. This may explain the engine transplant. We can share some resources for parts that will most likely ship to you. We hope the best for you and will be here to help you out if you buy the car. Good luck and again, nice car.