can Porsche 968 3.0 litre engine fit in 924 body?

yes. the 924s engine bay is bigger than a 968s.

Yes, but not because the engine bay is bigger or smaller, it's the same platform. The 944 is basicly a "widebody" 924, modeled after the 924GTS race car. The 924S, (which was the last run of the 924) shared the same exact powertrain with the base 944. The second generation 944 (1985.5 and up) added improved braking, suspension and added more powerful engines like the the turbo or 16 valves but did not change the frame.The 968 was originally going to be called the 944 Gen 3, but Porsche decided to change the name to help boost sales. Body panels were changed, but a quick look at the interior and under the hood lets you know the platforms were identical.A word to the wise: Don't bother dropping a 968 engine into a 924. Why? because along with the engine, you would have to replace:The wiring harness and ECUThe torque tube (to handle added HP, plus doesn't match)The transmission (the "snail" tranny in the 924 will implode)The brakes (woefully inadequate for increased weight/speed)The suspension (original 2.0L engine weighed a lot less)Front and rear spindles (convert to 5 bolt pattern for extra HP)The exhaustNone of that comes cheap. This is a Porsche. Even if you were able to do it, the cost of parts alone (No labor cost) would be in the thousands. I havent seen a used 968 engine on eBay for less than $3500. The 6 speed 968 tranny on eBay is another 2-3 grand. The worst part is when you are finished, you would still only have a 924 with the older, crappy interior and no resale value whatsoever.All said and done, for what it would cost you to convert your 924, you could have sold your 924 and bought a fair condition 968 coupe.

I would put it into a 1986-87 924S, but not the earlier ones.