First, ask if you’re even fit enough to get through the marathon training block. With a 25 mpw base and no prior knowledge of your athletic history, it seems you can get through Pfitz 18/55. There will be a long run work out around week 15 where it’s around 18-22 miles long and 10 of those mile are at marathon pace. If you can complete that workout then there’s a good chance you can complete a 3:45 marathon. Good luck!
First, ask if you’re even fit enough to get through the marathon training block. With a 25 mpw base and no prior knowledge of your athletic history, it seems you can get through Pfitz 18/55. There will be a long run work out around week 15 where it’s around 18-22 miles long and 10 of those mile are at marathon pace. If you can complete that workout then there’s a good chance you can complete a 3:45 marathon. Good luck!