Stupid question. Is an isolator necessary to race at most tracks? or is it a precaution just to avoid potential leaks?
Most mechanical guages come with AN fittings and if they are plumbed correctly I would think that a leak would be rare.
AN fitting rarely if ever leak if they are installed correctly. From my experience working with aircraft engines, most would probably be surprised how long they run before fuel lines or any AN fitting is re-torqued. Not only that, most see significantly higher pressure than the 5-7 psi from a mechanical pump.
If it's gonna go inside, use the isolator. The leak potential isn't just from fittings,... gauges CAN/DO fail internally. I see it at work quite frequently. Also, God forbid you find yourself in an accident. The last place you'd wanna be is trapped inside with gas being sprayed all over.
Might sound extreme, but them's the facts. Be safe.