I am installing boost/vac - electrical fuel pressure gauges...

I want my gauges lights to dim with my stock gauges. So I should be able to tap my white wire with the gray wire from fusebox labeled "INST" right?

To power my FP gauge I use the wire labeled "GAUGES" on my fusebox?

What’s the best place to ground them? Can I ground them with an existing ground wire?

Any help would be appreciated