I will try to put this nicely, but, planning a cam swap on an unknown-to-you engine that’s in a car you don’t own yet is putting the cart a looooong way before the horse.
Your new engine may already have a cam in it. Or your new engine may be a 7.5:1 compression factory dud that can barely support the stock cam in its current configuration. Or maybe your new car ends up needing $1k in brake and suspension work you didn’t realize until you put some miles on it and a cam change isn’t in the budget anymore.
Doing some research ahead of time is good, planning upgrades on a car you don’t own before you know it’s other needs is silly. And no matter how nice the car is or how well you check it out, you will find things that need to be addressed after you bring it home. Needless to say, what those things are will be specific to the car you bring home.
True double rollers are great, but if I bought a new to me Mopar with a 318 and it ran decent the timing chain wouldn’t be my first concern. Hell the cam wouldn’t be either. Drive it, check more things than any seller is gonna let you check, drive it awhile more, check more things, then maybe start planning upgrades.