I am moving over at least partially from cycling, lots of road races and crits (almost a cat 2 racer), to running my first marathon in the fall. How many weeks of training will I likely need for prep time for a 3.5 hr marathon? Any major issues I should be aware of?
16 to 24 weeks is the norm. My advice: Build weekly volume (miles) slowly! The book “Daniel’s Running Formula” has a lot of good advice I wish I’d have followed starting out. Good luck!