Low fuel pressure light, take blue/white wire off off switch (down by fuel filter) and, with the key on, ground wire to engine block. Light should come on. If it does, odds are switch is stuck in open position. If it doesn't then it's bulb or wire that's bad.
For temp gauge, same thing. If gauge pegs with key on when you ground the wire it's good. If not then it's the gauge or wire that goes to the back of gauge. I got another cluster from a friend and swapped the 2 gauge cluster into my unit. It now works, but temp reads high. The gauges are not very accurate.
You can sort of test the sender by reading resistance from sensor spade terminal to engine ground-don't need the key to be on. On a cold engine it shuld read close to 1K ohms. It reads progressively lower resistance as the motor warms, but I'm not sure of the temp-resistance scale. I just ordered a new sensor for my gauge in the hopes that it will show a more accurate reading. Switch and sensor about 30 bucks.
I have much the same problems as you - stuck (non-working) temp gauge, fuel pressure light I'm working on (my sensor works, but the light isn't going on). I've got a 74 GTV. If you discover anything when working on the gauges, I'd be much obliged for any info. I won't be addressing it for a few months, I figure (I have a few other things ahead of it on the list).