temp, alt, oil pressure gauge ideas

First question is, the water temp mechanical or electric?

Been a long time. I think B/RB has a second oil pressure tap, someone will have to confirm, but otherwise just either tee in or replace the stock sender

The waterpump on B/RB "I think" has an extra plug. Mechanical gauges are a paradox. They are all proprietary, and all use a mount/ mushing that must be used with the sender connection. But if you dig around, some of these come in smaller fittings. I think 3/8 NPT is the smallest I've seen

The amp gauge is going to be a problem as the factory wiring is "already" a problem. The basic "thing" with an ammeter is, that disregarding the starter, you want the alternator and all loads on one terminal, and only the battery hooked to the other.