Water boiling question

Hello All. I’m getting ready to brew a “Fireside Ale” from William’s Brewing. The instructions say to boil 4 to 5 gallons of water for the brewing process and I don’t have a pot big enough for that. I can only get about 3 to 4 gallons in the pot that I currently have. 4 to 5 gallons would be pushing it because it wouldn't leave enough room for a good rolling boil or room for the foam to rise during the boil. Just wondering what everyone’s thoughts were on using 3 to 4 gallons versus the recommended 4 to 5 gallons.

(Time to buy a new pot )

I'd use 3 gallons for extract brewing. With that, you won't get boil over with your current pot...and it'll be easier to cool your wort with cold top off water.