Mother of all Block and Tackle

[Kiantone3]

I am about to build a hopefully cheep block and tackle using 120' of 3/4" cable and five 15" wheels and hubs from old hay wagons. I intend to weld three hubs in line to a heavy 3" "C" channel and the opposite two hubs to another piece of channel. I intend to have a strap come from the channel to support each castle nut on the hubs. My question is should the hubs be arranged in a "LLL" and "LL" configuration or to get the distance between the wheels less two pairs of the hubs could face each other. This would make it imposable to remove the wheels. Am I over valuing having the wheels close? I would hope to have twenty feet of cable between the blocks to start the pull. Pulling out tree stumps four foot tall and 5 inch to ? inch in diameter with 90 horse four wheel drive tractor. What is the weakest link? Thanks for any advice.