I grew a 615 lber last year.
I think vine management and pruning helped quite a bit.
I foliar fed the plant once or twice a week.
I'd recommend at least one of Don Langevin's books on the subject, as I learned from these as well. They are "How To Grow World Class Giant Pumpkins" There are three volumes. I have volumes 2 and 3.

Douglas

thankyou doug,can you tell me where i can get hold of these books.also i know you cant swap seeds from usa,but do you know of any where i can get good pumpkin seeds.