It's a little low for spec - my LT1 gets ~47.5-49 PSI with key on, car off. At WOT my FP goes up to 50psi. While I don't know if it's 100% the pump at fault - it does seem like it's consistently lower in all your tests than it should be...

 

The dyno sheet is useless without AFR results. It is all speculation without them.

 

True that - the guy who did my dyno runs immediately diagnosed the fuel pump when he saw the AFR linearly going up as the RPMs went up. Got a pressure gauge on it and sure enough - WOT the pressure dropped to 20psi.

 

Your printout was STD and not SAE. Have them do SAE and see what you get, then you'll be able to see if you low or not. Also FP should be 43psi.

 

i've got a very similar setup as yours put down 340/350