Steve, I can't see how your truck could possibly weigh 5000 pounds. I'm pretty sure 3/4 ton trucks were in the 3500 lb range, plus or minus a hundred.
The big block engine actually weighs pretty close to the weight of an inline stovebolt engine, so I don't see that as a source of weight gain. I can see if you converted it to 4WD, but I would think that would still only tip the scales at 4000 pounds or a little over.
So I would imagine that EVEN with your switch to taller 3.73 gears, you will have FAR more performance than your old truck had, because of a ton less weight.
