Should the sender be the first thing off the seawater pump or can it be anywhere in the system, ie, behind intercooler, fuel cooler. Raw water cooled system.

Most are in the block itself

where in the block?

Many run a small water tube (no sender used) from the intake manifold to the dash gauge. Livorisi's dealers should have parts, tubing, fittings you need.

I have one and it's on the PS cooler after the intercooler and fuel cooler and ahead of the oil cooler, question is does it matter where the location is in the system for an accurate reading?

Install it in a port on the intake manifold if you have one. The other option is to install it in one of the block drains. If its installed in a block drain, they tend to clog easily from sand and sediment.

My block drains will clog halfway through one season. I put mine in my intake under my T-stat.

I just replaced my old 1/4" tube pressure gauge with a new livorsi with a 1/16" tube(guessing on size) mech. pressure guage. The old one used a modified block drain fitting and was totally clogged and useless. I'm moving the new one up to the intake manifold.