Long Distance Cycling during Marathon recovery?

Ok, I am in a bit of a quandary. I am training to run the Desert Classic Marathon on Feb. 2nd. 2 weeks later on the 16th is the Casa Grande 300k brevet. Now, I have ridden the brevet series for the past 4 years and would like to get at least 1 brevet in. I figure the 300k is probably the best shot as the 400k even though it is a month later will likely be a bit more than I can bite off with as little training as I will be able to dedicate. I am pretty sure I could turn out a liesurely 300k without too much trouble but the question is can I do it without problems 2 weeks after a first marathon? I think if I could get my glycogen replaced since it is a non weight-bearing activity (particularly since I ride the Ultra-Cycling distances on a recumbent to save the pain in the backside). Am I wrong in thinking if I remember to spin and take it easy in the hills this would be doable?