About the same Jeff, to a P-51H that is. Which has quite a bit bigger wing than what the P-51D wing is. I've got a plan to use an FJ-1 wing to do a tri-gear Mustang ----
The XFJ-1 had wings just like the P-51H, later FJ-1's had a much larger wing root leading edge extension than what P-51's had but also the trailing edge of the wing got a kink to it, from the inside end of the aileron to the fuselage where the flap's chord is longer. You can see it in the pic I posted of the FJ-1 wing on the F-82. Although Wiki says the XFJ-1 got wings from the P-51D (and the tail and canopy), comparing my model's parts, it clearly wasn't. If anything, the wing, tail and canopy came from the XP-51F, and I've got a plan to reverse engineer the FJ-1 parts to do an XP-51G (bottom pic). All I was waiting for to complete this was an FJ-1 canopy, not the one you see in the pic, where photos show that the canopy sat on top of the fuselage (like the FJ-1) and not set into the fuselage like earlier P-51's.
For sometime I had been wondering why the XP-51F and XP-51G had such a huge canopy. Then last year or so, I came across some new photos (to me anyway) which went a long way of explaining the why. It would seem that NA raised the cockpit upwards (I suspect it was because of the same reason Spitefuls and Furys (Hawker ones) had raised cockpits) and the larger canopy was needed for head clearance. The P-51H had a raised cockpit too, but instead of giving it a bigger canopy, the fuselage sides were built up in metal and a regular P-51 canopy was used.