My water pressure line is on the block and keeps getting stopped up with trash, can I get a reading here on the water lines going to the headers...

May be lower there

There is another plug on the oposite side of the temp sender would it be better there.

Yes, that is an acceptable place to put the water temp or pressure sender. If you are going to run a small water line (mechanical gauge vs. electrical) to the dash, it might look nicer to run the line from the rear of the intake manifold (brass plug in your picture). Another option is to switch your water temp gauge to the front fitting. Lot's of choices on the Brodix manifold.

That would look better running it under the manifold, there is a bigger plug in the right rear but I couldn't budge it.

If you use a 6 pt socket with a 6-12" extension and a breaker bar that brass fitting will come out

That 3/8's ratchet I had on it fell short.