Engine options for swap to 66 Suburban

[suburban509]

I've read and searched this forum for hours and still wonder what might be the best LS engine and transmission to put in my Suburban. I'm going to try to find a complete package at the salvage yard with trans, harness, etc. Plans will be to tow around a 5000 pound camper long distances. I assume that a 4.8 is just not going to be good. So it looks like its between a 5.3 and 6.0. The 5.3 being much more affordable. What would/have you used for this? What year range engine is a better choice? Will a 4l60 do the job? I have a recently rebuilt 4l80 from a 97 Suburban that was hooked to a 7.4. Do the big block transmissions bolt to the small blocks? Year range for transmission compatibility? Thanks for any opinions.