I find the endorphine rush that accompanies a good workout only serves to delay the sleep even worse. Much like the OP, I find it difficult to sleep before 2:00 or 3:00. I can sleep fine from this point until 12:00 the following day, but if I force myself to conform to a "regular" schedule, sleeping at 2300, and waking at 6:00, I am typically groggy and incoherent until well after 11am. On mornings when I can gather the mental energy and focus on a good workout, I'll awake at 6:00 and run a few miles or do some calisthenics. Nothing too complex, as usually at that time, I lack focus or coordination to do anything beyond the most simple exercises. Anyway, the resultant endorphine rush is like a natural cup of coffee; It wakes me up.
In contrast, doing a workout not long before bed causes one to also shower. Showering before bed time for me, at least is a huge no-no. I WILL NOT fall asleep until well after 430! I"ve attempted this a few times, and was faced with a full 8-12 hour work schedule the next day and things were not pretty.
Melatonin pills, a bit of white wine, some higher quality vodkas, and/or a bit of sexual activity (when the lady is around) all seem to work. I just hate being codependent on some outside stimuli to fall asleep, but until one can find a job that allows a 12:00 schedule, this is the way it has to be.