Yes you can. Just make sure you have the correct shaft configuration and is a small block. If I am correct, the shaft of the RC10gt is a short threaded shaft or SG crank.
If the duratrax engine you have is a small block and has an SG crank, you'll be fine. If it's a long shaft, you'll have to get it cut to the length needed.
You just need to transfer the flywheel, collet and clutch assembly on to your duratrax.
The problem that can arise is is one is an sg crank and the other is a threaded shaft. That can be resolved with the purchase of the proper clutchnut.
In a nutshell, yes you can use that engine. Just remember that with an .18, you'll have trouble keeping the front down.