I'd say there is another issue here. Maybe the winch brake is dragging... (Is it possible a rear axle is hung up on a stump?)
I would think (without seeing the actual situation) the stock winch should be able to move the truck, single line, at idle, not driving, without problems.
Snatchblocks/doubling-tripling the line would be for much heavier loads.
Have you done your calcs re how much pull you need to move the truck.
You are not pulling the weight of the truck - it is on wheels - just use it's weight for calc purposes.
How deep is it stuck in the mud (what you have to pull the rear tyres through)?
What angle are you pulling it up?