This is on a 2002 c5...but ls1 motor so doesn't really matter.

Im looking to add a fuel pressure gauge. I was going to mount the sending until on the fuel rail port but that port is already in use by the nitrous fuel solenoid line.

I was wondering if its advisable to add an adaptor with an port for the sending unit? should I find an adaptor and tap the sending unit somewhere else?

this is the adaptor I have... http://realstreetperformance.com/s.nl/it.A/id.88261/.f

has 1/8npt ports and 4an ends. Will this work? Or would there be too much "weight" on the end of the fuel rail?

 

That should work fine. Here's how mine is setup. The sending unit is "I" and it reads the same as the mechanical gauge that I have at the end of the driver side fuel rail.