When the OP said "regular fork", it's unclear whether he/she is referring to a fork from a single bike instead of a tandem fork or if he/she means a threadless fork instead of a threaded fork. If it is the former, then you have the answers above (i.e., not recommended unless it is an extra beefy single-bike fork); if it is the latter, then the answer is yes, you'll just have to change the headset and stem at the same time as you change the fork, but this shouldn't be too hard.