I haven't worked on a '99 but for the return fuel system of an 03, you can expect 63ish for fuel pressure at WOT.

Here is some info on my LQ9 when I was NA. I had a fully bolted 6.0L with stock injectors (UD pulley, LT headers-HF cats-xpipe-dual flowmasters, 160 thermo, CAI, E-fans, 216/222 cam springs Ti retainers, ported stock TB w/ bypass, 3000 stall converter, tuning). I put down 35x/36x (Hot day) on the dyno with 92% IDC.

Just some info

 

Thanks Krambo...the stock injectors are around 24# correct? If so, I feel better about using what I have. I think I'll get by, but I'll probably be in the 90's for IDC. I guess that no matter what I'll give it a shot, since my budget is in the negative right now. Still have to put a trans in the truck just so I can drive it to work in it's current configuration, then I just need the cam, some lifters, and gaskets and head bolts to get the LQ9 together. Maybe an oil pump but my current one puts out great oil pressure, only has 60k on it, and I haven't heard of too many oil pump failures so I figure why mess with a good thing?

 

keep the oil pump, I don't understand why people change them out.