1996 k1500 5.7 need suggestions and some wise advice on diesel swaps

Hi I am new to wanting a diesel i currently have a 5.7L vortec in my truck with 127k on the engine and 300k on the body. Ive always wanted a diesel but I dont know the route to go. I would love some expert opinions, on the best direction to go for the truck. I recently decided that I didnt want to get a motorcycle instead i wanted a diesel in my truck. I dont know much but the information i would like would help me out. I would like something with a little power maybe a 6bt naybe a 4bt depends what I can find. I have been seeinf that there are conversion kits to fit tbe 4bt and the 6bt to convert to a 4l60e tranny.

I think a 6BT is too heavy for a 1/2 ton Chevy IFS, and the 4L60E/700R4 won't hold up too long.

A 4BT would be a better fit, if a Cummins is a must.

Otherwise, a 6.2/6.5 would be a bolt-in, and parts/info would be easy to find. Properly put together, a good 6.2/6.5 conversion would deliver 20+ mpg with 24-25 a real possibility.

Jim

Im currently looking into sourcing a cummins 4bt and think I am going to go with these guys. https://www.4btengines.com/used-engines/ They do remanufactured and used along with new obviously with all sorts of guarantees which make me trust them more haha.