My Quistion is why not go with a 501 caddy motor?
You've got some heavy steel there and it's gonna take alot of torque to get it rolling.
The early 70's 501 caddy engine had 400 HP and 550ft. pounds of torque,
and they got decent fuel milage in stock form.
And they have companies out there building fuel injection systems for them and all kinds of HP stuff now, if thats what your in too.
Just not sure how well that small block is gonna pull that tank around.
Kurt