managed to get a nice set of rally gauges to replace the fuel/idiout lite setup. What wiring changes will I need to do (anyone have a diagram of each)?

Ammeter - hmm different connection to regulator?
Oil - new sending unit, added wire?
Fuel - should be OK
Temp - new sending unit, added wire?

Anyone done this, I am just about to re-loom the harness under the dash so now would be a good time. The old harness looks surprisingly unaldulterated, pliable, and the continuity seems good (that's a mouthful).