George W what year is your truck? Post filter would be best then you can tell when your filter is getting old, you should show a slight decrease in pressure. Yes this would be a good spot, basically anywhere after the pump will help, I think just having the gauge is important. When I put mine on I found out I was running 6psi and 0psi open throttle. Not good. Cant speak for the Westach because I use Auotmeter. I'm sure someone will chime it with more info. Good luck.
Gottorq, the snubber line is a 18" or so piece of hose the will remotely mount your sender off the VP to help reduce pulsations and extent sender life, also you can add a T valve to shut the line down almost to nothing to reduce more of the pulsations. This will also extend your sender life and smooth your gauge out. Good luck.