Beowulf,

It would be the same as if you were building it for flight. If you build the kit stock, per the instructions, you could later drop your engine/fan combo in. The instructions ask you to use the fan unit to align the inlet with the fuselage. I've done it that way, and I've installed the inlet without the fan present. When I didn't use the fan, it was close enough, but I put the fan inside the inlet, heated the back of the inlet up with a heat gun, then tightened down the fan to the fan mounts. It was good-to-go.

If you ever have designs on flying it, build it stock from the get-go. That kit is made of a polyester glass that you can see through. Once you get paint on there, it'll be harder to retro-install anything at all.