I've never brewed pumpkin ale out of a can. My first batch I used a 4lbs pumpkin. Cut in half and bake for an hour with brown sugar. Scoop out one half , mashed like potatoes, and put in the liquor and steep with specialty grains. Scoop out second half and put in the primary.
The 2nd and 3rd I used an 8lbs pumpkin with a cup of dark brown sugar in each half, roast for an hour at 350. Scoop out and put 3/4 in the liquor, steep grains, then use the rest in the SECONDARY. You will lose some wort to sediment so adjust the volume to 5.75 gallons for a 5 gallon batch. The roasted brown sugar lends a superb taste, one you will not get out of a can. I did three batches last fall and have 12 bottles left. But that the joy of a seasonal brew, you always look forward to it next year!
P.S. this was an extract recipe.