Not sure what you have to work with or what kind of a trailer you are loading it on. I always had a winch tractor and would load dead tractors backwards, either winch them over the beaver tail or over the front on a removable neck trailer. When your D8 is at its highest point before over centering (which ever end you are loading on) the ground will force the dozer up, stop and chain it up to the hardnose. This works if you are winching or towing with another unit, on hyd. or cable dozers. Always put a boomer in your chain holding the dozer up so when you go to remove the chain you only have to block the dozer and not lift again to remove the tension off of the chain.
Good luck, Garry