Dodge D100 project "Grim Sleeper"

You can get a cheaper 360.

the 340 will be ok, but again, if you can get more cubes, that is going to be the most practical way to get this truck moving.

The 360 is going to be better, because of it's stroke against all of that weight. Getting this thing to move quick from a dead stop is going to take something to the tune of 500ft lbs. Start thinking big torque. HP isn't so much of an issue. It will come with TQ. 350 HP and about 400 TQ is going to put that pickup in the mid 14sec 1/4 bracket somewhere.

If you want to keep a small block, gap the rings big for heavy load. That will give you the opportunity to supercharge, as well. The route I'd go would be small block 440, iron magnum heads, supercharged with about 12lb boost. That should feed somewhere around 500hp 600tq lazy without breaking things. Set it up with std. hemi gears on an 833 with 4.10's and you'll start dropping jaws.

If you want cheap HP, go 360 and stroke it. same deal. Supercharge, big ring gap. Might land you close to 500TQ. Start thinking about tires and possibly weighting the rear or 4 link. If you don't want to spend the time or cash on boost, you can always hide a bottle.