If they both had the same length barrel would they be the same length or would the take-down version be longer - if so, how much length does it add?

I've been watching your post remain unanswered so I got out my tape measure - no real difference in length. My BLR in .358 Win = 42" w/ 22" bbl; my BLR in .375 Ruger (Shilen 24" bbl. added) = 42.5"...
I'd highly recommend the takedown, its easier to travel with & more versatile. Best bet would be to get a GOOD gunsmith to tweak it so that it truly is MOA upon reassembly, as is mine. And get a trigger job!

Bill,
They normally are the same, there may be some exceptions but I have not seen one..I see no reason for extra length as it would be counter productive to the action itself.