I've posted this before and several of you have commented on the utility of it. This is my garden cart/wood cart. It's made from an old wheelchair.
Wheelchairs are typically designed for a 300 lb. load capacity but since they carry humans there is a 50% overload factor built in. So a typical wheelchair will carry 450 lbs.
I put the handle over the small swivel castors and let the big wheels lead the way since they are better for rolling over rough terrain. I put a tailgate on the front end for when I'm hauling soils or topping and wish to shovel out of it.
This thing pushes mush easier than my heavy duty contractors wheelbarrow. At a recent volunteer event at our local disc golf course I brought both the wheelbarrow and the garden cart. Everyone loved the garden cart. Over rough terrain one fellow was pushing the cart with one hand while smoking a cigarette with the other. You can't do that with any wheelbarrow.
It wasn't a difficult conversion. I did it in a couple hours with junk I had lying around - except for the gate latches which I had to purchase. You can find one cheap at an auction or estate sale or even on Craigslist.