Having spent my early years in Rhode Island, I understand the "tin worm" is highly destructive. Some cautions on an Aluminum bed. (1) They are easier to damage than a steel bed, so depending on what and how yo throw in a load, it might be a concern. (2) They are more difficult and most costly to repair than a steel bed. (3) Because of # 2, Insurance premiums can be higher.
If it's just the bed that is shot, a bed replacement might be in order. Shops that replace beds pickup beds with flat beds might have replacements.
It sounds like you do not use as a daily driver and the driveline is probably in good shape, so if the body and below are OK, a bed replacement would be a lot cheaper and you could keep the manual gear box.