I would say 4000, no way. 3000, maybe low to the ground but unloading from a trailer I don’t know. I never had a 320 but have had a 328d. Safely lifting 4000 with a 328d was even a stretch. It would do it but had to be careful. I’m sure someone will say they do it all the time but do you really want to trust something that is maxed out for lifting with a full pallet of seed or tote of chemicals? I feel you need something bigger or get a forklift that is made for lifting.