I am not aware of any time limits. As long as no "high" capacity magazines are involved, and it isn't otherwise prohibited here (like the taurus judge, which is considered a short barreled shotgun) it shouldn't be an issue. Your FFL should be able to verify the legality of anything you want to do. If it isn't kosher, no FFL will do it, so if he/she will do the transfer, you'll probably be okay.
*I'm not a lawyer, but I believe this to be accurate.