Auto to manual transmission swap

[C20Chevy]

Hi, I own a 1970 c20 camper special, I am the second owner of the truck and it is completely original with a 350 small block, the th350 transmission just went out on it. And I am looking to get a new one put in, I always kind of wished the truck was a manual, so I am considering swapping to a manual. I didn't know if anyone would have any idea how much it would cost me or what transmission I should be looking at putting in, I do use the truck for towing.

Thanks,
- Mike