Testing oil pressure on a newly rebuilt engine

Last week I was ready to test start my Montero, (I have a "build thread" on this but I haven't been good about updating it - https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/91-montero-refresh/183386/page1/ - after replacing the block with a new old stock short block and then fitting it with reman heads. The factory oil pressure gauge has never worked reliably, so I wasn't going to count on it during the test start. After spinning the motor by hand to make sure it spun freely, I started and ran the engine just long enough to verify that it was in time and running correctly. Then, I shut it off and cracked the oil filter loose to see that the oil pump was sending oil there, and I got a stream of oil from the filter when I loosened it, so that's a good sign (I think). I've only run the engine for a matter of seconds so far, because it took me so long to rebuild this thing and I don't want to wipe it out in the first minute.

I found this: https://www.summitracing.com/parts/sum-899004 - which I could theoretically plumb into the NPT fitting where the oil pressure sending unit usually resides. Should I pick up one of these test kits with a long enough hose to read the gauge from inside the vehicle, and trust it to give me an accurate oil pressure reading? Is there anything else I should keep in mind? This is really my first engine overhaul, and though I replaced the heads and put everything back together, I honestly couldn't tell you the process by which oil flows from oil pan to overhead cam. This project has been a real learning experience and I'm hoping to not turn it into a sad ending. 

You can also just get any old super cheap oil pressure gauge and plumb it in. 

On a brand new engine (or any engine that hasn't run in a long time) I'd be tempted to disable spark and fuel - even removing the plugs maybe - and spin the engine on the starter until I saw oil pressure on the gauge. 

If you see oil pressure on the starter, you should be fine to run the engine and make further checks.

For example the middle gauge in this. You can probably find them for $10

https://www.harborfreight.com/automotive/automotive-accessories/interior-accessories/electronic-triple-auto-gauge-set-41017.html

And if you don't want to risk using an HF gauge, I suspect most local parts store will stock a cheap Bosch or other brand name mechanical gauge, and they are usually only around $20.  I use mine to test with, but then use electrical gauges in the car once I've verified it with the cheap mechanical one.

Agree with the suggestion to pull the plugs and disable spark/fuel and spin the engine on the starter to get oil pressure.  I also do this with new motors and even swaps and wham adding something like an oil cooler.  

Good idea disconnecting the ignition before testing. I called a friend and he had the oil pressure test gauge with a 4' line, so I can watch it from inside the truck. If the rain ever quits I'll hook it up this weekend and give it a shot.