Kevin as long as you are flying from a well prepared sealed strip the P-70 should fly it just fine. You could find the after the first couple of flights you maybe able to lighten up the fuel load a little also...
I have been flying a big Fiber Classics (Comp ARF) Mig-15 for a number of years now with a Wren Super Sport which should be quite similar in the thrust department as your P-70. Top speed for my Mig is a very scale like 120 mph and she does fly more on the wing than thrust, but is definetely not underpowered or sluggish in my opinion. Take-offs are also a non event with reasonable roll distances. I would say give it a go as it will fly comfortably in a scale like manner in my opinion. Both the Mig 15 and the F-86 fly very similar on same thrust turbines. The P-70 as with the Wren Super Sport are working harder than a big turbine and will be close to max rpm more often than not for much of the flight but thats no reason not to give it a go and see if you like the scale like performance...
I have also flown both the Fiber Classics and the FB F-86 extensively myself with a 30 lb thrust turbine, and they both were way over powered with the bigger turbine with most of the flight around 1/2 or less throttle. The FB F-86 is smaller and lighter of course so the P-70 I would have no hesitation in recommending for this 86...
Probably the Merlin M-90 would be just about the "perfect" size and power balance for the FB F-86 and their new Mig-15 in my opinion.
P.S. FYI If I remember correctly Wolfgang Khlur won the very first WJM flying a "larger" 1/5 scale Fiber Classics F-86 powered by a Sophia J850 with approx 11 lb thrust!!! So the smaller FB 86 version with a P-70 installed will be a safe bet
Cheers- Marty