Dunno how much help I'll be but it couldn't be any worse than what everyone else has recomended...
The setup sounds good. Most clustering solutions I have seen use identical hardware for each node. Typically I've seen clusters set up with a host node and slave nodes. You start a job on the host node and it will divide the work around to the slave nodes. It sounds to me like you want to use a clustering solution similar to what I've seen with VMS where the nodes are peers and typically one node will run the job and if it dies the other takes over.
What distro...
I think that is up to you. For some reason Redhat 7.3 is popular but it's getting old so I would go for something newer.
Clustering software...
Like I said I'm still new at the clustering software deal. There are a few comercial Linux Clustering vendors out there but usually they develop their own solution. I have installed ROCKS but it was kind of strange. (used the host and slave node architecture)
Good luck