Fargo time and Marathon analysis?

I was on long run today and started thinking what should my pace be for Fargo and what did I think my finish time would be? Then I went back and looked at my log and I chose to review my past marathon race times and I saw an interesting trend.

Do others who run trails and then do road races have the issue of not knowing how to translate the pace?

Here is what I noticed looking at my past stats.

Marathons 1 - 15 (1993-1999) - Age: 36-42 Weight: 180-190 - Avg. Yearly mileage 1200

Avg time 4:30:18 - Min 4:02:33 - Max 5:09:46 - Std Dev 19:02

My max time was run in 1999 at Grandmas, I ran with torn cartilage to keep my streak going. After that marathon I had surgery to remove the tear and then had the following results:

Marathons 16 - 22 (2000-2002) - Age: 43-45 Weight: 190-210 - Avg. Yearly mileage 850
Avg time 5:11:07 - Min 4:42:29 - Max 6:01:58 - Std Dev 31:58

The max was in Nashville where we got to experience an 85F marathon, our hottest training run was 65F. The joys of running in Minnesota.

My conclusion, my knee surgery in 1999 did set me back, I gain around 10+ pounds and didn't get back into the same training regiment. The end of this period was marked by the end of my Grandma's steak in 2003 and another knee surgery. I tore cartilage playing soccer and failed to get into Grandmas that year which kept me from running another marathon with a cartilage tear, probably good. I also gained another 10+ pounds after the surgery.

Marathons 23-27 (2003-2007) - Age: 46-50 Weight: 210-220 - Avg. Yearly mileage 800
Avg time 5:22:04 - Min 5:03:34 - Max 5:52:48 - Std Dev 18:42

So my analysis concludes it may be age but my guess is weight. Which pretty much goes to lack of training (ok eating too much) which could have been controlled by training 4-5 days/week for 16-22 weeks.

My weight is heading down and the mileage is creeping up (by Fargo s/b under 210 - mileage > 400 and I expect by Fall to be under 200 - mileage > 900) as I have gotten myself rejuvenated through the trail races and the quest for 50 states.

So in looking through these stats my goal for Fargo is to break 5 hours if the weather is good (cool - no wind), the course is fair and I don't do anything stupid. If I don't break 5, I'm ok with that as I will once again as I continue to train, stay healthy, eat right and lose weight...........