Specific Oil Viscosity Question...

[MidOHasp]

I know this topic is discussed in about 8 gazillion threads already, but I wanted to ask as specific of a question as possible rather than "what oil viscosity should I use?"

Application:
408W, built to considerably "loose" clearances
10.25:1 C/R
Run on mix of 94 and 110

Current Oil:
Mobil1 15W-50 Performance Driving Formula
Standard Canton Oil Pan (not race "T" pan)

Characteristics:
Cold Start-Up, 55-57 PSI, steady, every single time
Hot Idle (Water = 180, Oil = 180), 22-25 PSI
Hot, Crusing, 40-45 PSI

The cruising pressure does not seem to vary much with RPM (if at all). Once you get it up over 2000RPM, it holds rock steady at 40-45 PSI (depending on temps).

Some people tell me "as long as you have pressure, you're good," and some people say you need at least 10PSI for every 1000RPM. Just put the 6500 chip on, so that's 65 pounds minimum. I'm 20 short.

I just picked up a case of Valvoline SAE 50 Racing Oil and a new Mobil1 filter for the oil change I'm going to do this weekend. Is this a mistake at all? Should it solve the low pressure issue? Should I even be worried about that pressure with fairly loose clearances?

I've seen some posts where people had good luck with Castrol RS Synthetic 10W-60, but where in the hell can you buy that? Red-Line claims their straight-weight 50 is like a 15W-50 and their 60 is like a 20W-60 due to its cold pour characteristics.

Seems like there are 100 opinions on this matter. Should I be worried about my pressure? If so, what should my course of action be?

Thanks,
JP