291 hemi useable/serviceable?

Yes, Bob Walker, the owner of Hot Heads is your guy. He can tell you all about them. The Desotos are good engines. I would get them both if you can. The smaller cubic inches is not as much of a handicap as would be with a non Hemi engine simply because of the heads. You can get well over 300 HP without a problem. Oregon Cams can regrind the stock cam core to one of many grinds they have for 75 bucks. That's who did mine and they did a real nice job. Just look through the Hot Heads site at what all is available. They also have a Hemi book that tells all about them and what all interchanges.