I have a sport model (RCM Terrier, balsa/plywood construction covered with Monokote or Econokote stick/shrink film) that I built in 1984, and it has somehow come through multiple moves apparently intact. I have a radio for it that's still FCC and AMA legal, as far as I can find out (though I'm certain the transmitter and receiver batteries will need replacing), but back in the day, power generally came via burning methanol, often with a small amount of nitromethane added, along with oil to lubricate the small two-stroke engines; electric models were heavy and performed poorly with their nickel-cadmium batteries and "can" motors.
In this case, my old engine is an O.S. Max .25 (appr. 4 cc), plain bearing non-Schneurle, good for around 14,000 rpm with a 9dx6p (inches) Master Airscrew reinforced nylon propeller. The model has a span of 60 inches (~193 cm) and weighs about four pounds (1.8 kg) with radio, engine, and a full fuel tank sufficient for 20-25 minutes of flight; when I flew it regularly it was mildly aerobatic, capable of loops (inside and outside), spins, snaps and aileron rolls, etc. -- but a little underpowered for the style of aerobatics that was common thirty-five years ago.
I'd love to restore this model to flying condition, but glow fuel is harder to come by than it was then, and even when current was recognized as messy (unburned oil would coat the model after a flight), noisy (even with a muffler on the engine), and I'd have to replace the tank and all the plumbing, as well as the engine, after this much idle time (hasn't been flown since about 1986).
I'm aware that most modern R/C is electric, using lithium batteries and brushless motors. What size/type motor, battery, and controller setup would I need to get similar performance from this model to what it had thirty-five years ago?