Probably an FP35
If you are sure that what you have is an FP-.35, I would only shorten the nose about 1/2" to 3/4" and not worry about the length of the fuselage, especially if this plane will be used to just learn the pattern. The stock airplane in the hands of an expert level pilot will fly well enough to score over 500 points every time out. You main interest will be just in making it straight, with no warps and generally sound construction. To check on how things will fit, lay out the engine on the plans, moved back about 3/4", and place a 4 ounce tank of some kind behind it with about 3/4" room between the engine back end, and see where the back end of the tank is , in relation to the leading edge of the wing.. If there is still some room, you should be all set. As you get closer to the point of flying it and checking balance, you have the option of using a tongue muffler, or an after market tube muffler if you can find one to help with balance. If it comes out a bit node heavy, that isn't the end of the world for a beginner and will help you out in the long run. As you build the fuselage, inlay a 1" square section of hard wood into the tail end under the horizontal stab, as far back as you can and still have it surrounded by balsa. Drill a nice 1/8" hole through it right in the middle, and install a 4-40 blind nut on one side, just like you would for the engine mounts. This will be a nice handy place for you to mount tail weight, should you need it. You can make or buy square lead weights in 1/4 to 1/2 ounce increments with a matching hole, then use a 4-40 screw to hold them in place. A think piece of card stock under the weight protects the fuselage, and in between any weights that you stack up will help absorb vibration. Make the bolt long enough to go through the blind nut on the other side and you can install a jam nut there also for security.
Get the model finished and ready to fly and then check the forum for engine set up for the FP-35. Basically a hot plug and 10-4 prop will get you off the ground on 60 foot lines. It's not that much different from the LA.40 and .46 set ups, but you just need smaller diameter props.
Have fun and MERRY CHRISTMAS!!
Dan McEntee