I have a few years experience working with car audio, and have tried a number of sound deadening products. So I'd first like to say, anything from dynomat is over priced and under performs. You're paying for a name.
Also, You have to be careful what you put under a hood because engine heat can cause many adhesives to deteriorate. Just because something is advertised as working under the hood doesn't mean it will last.
As far as behind the engine, do not stuff any type of deadener back there. Your best bet is a ceramic firewall coating. The best one I know of is made by SecondSkin audio
http://www.secondskinaudio.com/thermal-acoustic-insulation/firewall.php
That won't deaden noise quite as much as a dedicated sound deadener product will, but it will take extreme levels of heat. You can then put traditional sound deadening mats or coatings on the cab side of the firewall if you want it quieter. (check out companies like RAAMaudio, SoundDeadenerShowdown, and again - SecondSkin. All three of these companies are great.)
I do know SecondSkin also makes a hood liner, although its mainly just a thermal barrier and will do little to block noise. So it may not be what you're interested in. They intend for you to put a traditional sound deadener, like CLD mats or visceolastic coatings, directly on the under side of the hood, then use a thermal hood liner to protect the deadener from heat. I have never personally done this and cannot comment on how well it might work. I can say I have always been please with SecondSkin products and wouldn't be scared to try something like this.
I know a lot of other companies make hood liners, and I'm sure some are great. I simply don't have any experience with them and don't know what to recommend. Of the deadening companies I have used and like, second skin is the only one that even makes a hood liner product so that's the only one I'm able to point to. You might try digging around at caraudioforum.com as there are a lot of guys on there with extensive experience with deadeners
Hope this helps.