I've got a hilly century coming up in a month and I'd like to put in a good, hard effort since I plan to ride with a group of fairly hard-core riders. I've done centuries before, including one with ~5000' of climbing, but I've always taken it easy to up to the final 20 miles.

Currently my endurance isn't bad. I can do 70-80 miles at a moderate pace (< 90% of LT). If I go hard (just below LT with some efforts above), my limit is about 45-55 miles. I expect I'll be in a small paceline of 4-5 riders for the century, so it'll be a lot of moderate efforts punctuated with hard efforts about every 5 minutes or so.

So I'm thinking of doing some 70-100 mile rides where I do a moderate pace until the last 30-40 miles and then try to maintain a hard pace or do intervals over the last part. Alternately I could try and do moderate rides where I lift the pace for 1 minute out of every 5, but I feel like I'd spend the whole ride looking at my computer instead of the road. I'm not exactly sure how to augment this during the week. Probably at least one good set of hill intervals each week, and one easy ride with some distance to it (maybe 40-50 miles).

Is there a better way to approach this? What kind of workout would give me the best "bang for the buck"?