I'm still planning on going big block, if only for the sake of having enough horses to get the big tires spinning. Mud requires horses, rocks require low torque, trails require a mix.
Rear engines can also allow better visibility, and protect the engine from alot of mud.
Here's a pretty general idea of what I'd be thinking about for a rear engine. Those are 49", it currently is on 54".
I do like the closed off occupants compartment, keeps the mud out! I'm not sure if I'll run those types of shocks, but I might (26" of travel).
Some differences:
I was thinking of putting the fuel cell in the front.
The wheelbase is a bit long for those tires. However since I plan on running 54" and 66/72" tires, a longer wheelbase would be needed to make up for the R1/2 or Terra tires added 9" radius but not as long as that.
Different axles (top loaders vs his front loader) so my belly will hopefully be 6" higher or so. He is running a 205 transfer case with the front output clocked straight down with it under the input. I plan to run mine flat.
Otherwise, that's fairly well the same idea I'm thinking of for a rear engine.
For the record, that buggy has about 66" of combined travel in the suspension. The shocks have 26" of travel.
I was wanting that much flex, but with a hydro over nitrogen shock setup so I could force the flex (lift/lower each corner individually), or be able to let the nitrogen work as an air shock when I didn't need it.