Anyone have any pointers to what I am going to need/expect for this job?

I want to install a few mechanical gauges at my throttle bodies on my 575s to check what my fuel pressure really sits at. I don't trust the electric senders. Any certain fittings I need? certain gauges that people like? etc...

Any help is appreciated, thanks in advance.

Like this?

LOONG time ago - this is going off memory.

You need a male to 2 female 1/8" tee and a small 1 1/2" FP gauge - I think I got mine from Jegs
http://www.jegs.com/i/JEGS-Performan...rentProductId=
http://www.jegs.com/i/JEGS+Performan...41364/10002/-1

Unscrew FP switch from fuel line elbow. Screw in tee and gauge on one side and switch on other. Don't think it took 15 minutes and worked well!

If I completely unhooked the electric sender and put my mechanical gauge in its place will it throw an alarm? Thanks for the pictures!

I think so, but not sure.

No alarm, I can tell you this because my port side was not working at one point.

I like the piggy back set up above. Keep them both and use the mechanical to verify. Be careful removing the stock 90 degree fitting, it is brass and breaks easy.

I got new 90's local, they were even blue

The T fitting BillR posted is best way to do it, so you don't have to remove the electrical sender.
The injection computer should be monitoring fuel pressure, and should throw a code. If pressure was low, this leans out motor and destroys it, so it's a critical parameter.

Triple300s, you don't have to install these to sell the boat is there a problem you're concerned with?

No, the sender is just for the gauge.