I was also told by VLM (or should that be VMLM) that they are definitely reviewing the GFA times and that the Race Director hasn't made a decision and that anyone close should definitely apply via ballot.
If you believe running calculators (which are normally based on experienced runners so dont equate totally to first timers) then a 39:47 with right training would equate to a 3:06/07 marathon time. So in theory as that was based on only 5 months training.....(BTW its around 38 minutes dead for a 3 hour equivalent run - but I know lots of 38 minute 10km runners who havent run a 3 h marathon)
But there is a world of difference between 10km and marathons - some can translate speed effectively as they race longer - others just can't. theres often no rhyme or reason. Get a decent program and start putting the sessions in and you will have a better idea by say Christmas if its a goal worth aiming for this year.
Your biggest obstacle will probably be injury from doing too much too soon.
In effect they can allow as many GFA people as qualify (especially the faster GFA people) without affecting many others as at that end of the race the field is relatively open. No point in limiting the number of sub say 3:15 runners as not many of the first timers (or club runners or charity) will run that fast. Its an argument for tightening the other GFA times at some point however but no evidence they will do that.