/6 or v8 swap?

If you have a decent slant and trans laying around it shouldn't cost much to throw it in the car to make it driveable. Then she could drive it around to see if it's bearable.

If she decides a little more power would be nice, it could be hotted up a bit with minimal cost. If she wants a lot more power, then the 318 could be swapped in.

Don't forget cooling, brakes, rear end, etc.

If she likes attention, talking to strangers at stop lights and car cruises, the slant will give her more than the 318 will.