I figured I should take the time to update this thread with what I have done/learned. In regards to the question about the bearing size, they are standard size, there was no machine work done, but the bearings are the hx size which has 0.001" extra oil clearance. I have them on mains and rods.
Before switching to a 50 weight oil I did disconnect my oil cooler and remote filter to make that wasn't the issue. I saw the same pressure. Pressure was also confirmed with a different mech oil gauge. Since then I switched to castrol 5w-50, it was all the local auto store had at 50 weight and I had plans to do some fun driving that weekend - I will be changing to a 15 or 20w-50 next oil change. With that oil in the car I drove it for around 40mins with rpm's > 4000, oil temp was up to 200-210, idle pressure was 15, red line rpm 50-60.
The redline rpm still concerned me so I spoke to ACL directly about the bearings and the oil pressure. ACL confirmed that the larger clearance will drop oil pressure which makes sense.
http://lubricants.s5.com/oil_pressure.htm not sure how creditable the link is but it is interesting, made sense to me and was inline with the discussion I had with ACL.
ACL Tech support looked up the sr20det specs, greater than 11psi at idle, and 47-57 @3200rpm. He said because there is no high end spec that my oil pressure was adequate for the bearings at high rpm - take that as you will but he seemed to be knowledgeable. Also recommended full synthetic oil - so redline or high end equivalent but warned the high teflon levels can cause issues with clogging oil screens and filters so you should be changing oil more frequently than with conventional... not something I plan on doing. I said i'll run mobile 1 or castrol which he said would be fine.
I went with the ACL's because they were recommended to be by someone that's been into sr's for over 10 years. It was also my first motor build so I was fond of the 1 size fit's all for reducing the difficultly. If I were to do this again I would likely go with oem nissan because it really isn't that difficult to size and my oem bearings looked great when the came out. On a positive note the engine is running great so I'm going to live with this and just keep beating on and hopefully it last a couple years before something fails.