the nova is a direct fit where as the force will require a bb chassis and a lot of drivetrain upgrades.
its hard to say which one is better ,the nova is a small block and makes around 1.8hp where the force will make over double that.the main differece is the nova will fit with no mods and comes with a pipe and manifold and wont destroy a stock drivetrain and will also yeild good run times , the force on the other hand will need a big block chassis to fit the truck plus you need a big block exhaust as the stocker will not fit plus you will need a lot of upgrades to the tranny and a 1/8 scale clutch, the list goes on.
long story short if you have the coin to drop on it go for the big block , if you want a reliable truck that wont break all the time go the nova.