Tempo long run?

I met the Magee's crew for a 6:30am run this morning. I could tell after the first mile this would be a 2 group run with one group going slower and doing 10 while the faster group would do the 12 mile route. Normally, I try and run my long runs in the 730ish pace to build endurance while not beating my body up too badly. Also, my long run is at the end of the week with 30-35 miles on my legs typically, and since leg day is Thursday, I'm usually pretty sore from lifting.
I knew after the first mile at around a 7 min per mile pace I was in for it today. Miles 2-5 were in the 6:15-6:20 range and I was feeling it. After mile 5 I decided I would be backing off a bit since I have the Bourbon Chase relay less than a week away. I backed off to around a 640ish pace not losing site of the 2 others in my group. Somewhere around mile 8 I caught them as they were feeling the pace as well. One of them had some very fresh legs while the other one is faster than both of us having just completed a half-ironman the previous weekend. Miles 9-12 were spent shoulder to shoulder as we ran through the UK arboreteum and campus. We ended up finishing the 12 miles in 1:20:30 which works out to a 6:40 min per mile pace.
Let me just say this was a very fast pace for the distance for myself. In fact, my half-marathon PR is only a 1:36, but then again I've only ran one and was dehydrated and vomiting at the end.
This has me wondering what my new half-marathon PR would be considering this run was on no rest, no tapering, and not even at race pace. I might need to find a half to run before the end of the year to see.