Okay, thanks to everyone for the input. I think if I were to do this, I'd use one of Sheldon Brown's solutions. Kommisar, what do you mean by "trail?" Are you talking about wheelbase? If so, I'm not as worried with an older frame; however, I will make sure to monitor geometry before attempting such a build--both bottom bracket height and top tube length. Anyway, for now, I was just trying to figure out if it would even be feasible before considering actually doing this.