hey snake...bought a 670 last year to replace the original thermoquad on a mildly built 360.
The TQ worked well but with the alum. intake I wanted an electric choke. I've never had a holley before (I have used TQ's and AFB's) but anyway it worked well right OOTB with a minor secondary float adjustment and maybe an eighth of a turn on the idle mixtures to tweak it. I used the factory secondary spring ( I have a 4500 lb truck - 355's)
it starts right up on fast idle , and runs well with no bog or hesitation at WOT
anyway I do miss the spreadbore carb and I think I may try a 750 street demon this summer as comparison
later, jim