I like the 2004R. Not terribly expensive to make reliable and will certainly hold up to the six cylinder engines listed above. In some cases easier to install because it is so close in length to the TH350. The bell housing makes it easy to bolt up to either the Chevy bell pattern or the BOP pattern.

A lot of folks sell them short, but they have always served me well.

And I like the 700R4 / 4L60 as well, though I find them more tempermental than the 2004R. But again, built right they work well and would hold up to any of the six cylinder engines above.

Just depends on preference and what your demands will be.

I put a 2004R in a 1950 Chevy 1/2 ton with a 350 V-8 in front of it and the customer was very pleased and is still using it after nearly four years.

I've run the 2004R in Cadillacs and not had any issues.

But everyone has their likes and dislikes. I like both and depends on what I am doing on which one I use.