I think you'd probably be better off at jumping in to week 3 of the 12 week plan (I don't have a copy to hand)- if I tried to go from zero to 47 miles I'd break. Week 9 also falls just before a cutback week. Given you've got 10 weeks I'd be inclined to break that down into two 4 week blocks (build 3, cut back 1) and then some sort of a taper over the last two weeks.
I've only followed this P+D plan once and had to improvise a bit as I realised the marathon I was doing was 3 weeks closer than I'd planned for. I did also replace some of the recovery runs with either spin or swim sessions.
Edit to add: there are some very active marathon training threads over in the Spring Marathon section, if you can run 3:40 for an IM , I'd suggest you go an introduce yourself into the sub 3:15 thread who will be able to better advise you.
with the fitness you're carrying over from IM you'll certainly be able to complete the marathon on 10 weeks training, it's just a matter of picking which bits of the P+D plan to use (the book is very good in explaining what each part of the plan is aiming to do).
I'm not aware of any trail specific marathon plans, but from looking at the map of the course I'd be making sure that any long runs include climbing some long hills.
I've used P20 factor 50 at both Lanzarote and Nice to good effect (although I did top up at Lanza in both T1 and T2 with other brands). The formulation has changed since 2004 as para-Aminobenzoic Acid (PABA) is no longer flavour of the month and they've also tried to make it less cloth staining (not a complete success on this one). Don't be shy with it when applying (even though it's pricey).
Adidas have a couple of new shoes (Boost and the bonkers looking Springblade) which seem to try to maximise "energy recovery". Are Puma working on similar lines or is this something you've looked at and decided not to pursue?