Thanks to everyone for their feedback on the topic of oil. It surely made for a lively discussion.
I emailed a few manufactures through their websites to get their take on the oil to use. I advised I had a modified 87 GN that gets driven 5,000 miles a yr and sees a few trips to the drag strip. Based upon those guidelines this is their recommendation for my vehicle.
SOPUS = Shell oil products making Pennzoil, Quakerstate and Rotella recommended Quaker State Defy 10W-40 or Rotella T6 Synthetic in 5W-40.
Mobil recommended their Mobil 1 0W-40 or their Diesel truck 5W-40
Royal Purple recommended their 10W-30 HPS.
I'm still waiting on feedback from Valvoline and Shaffer oil on what they recommend. When I'll receive I'll post their responses. As a new member I appreciate everyone's feedback and the rational they but behind their beliefs.