If there's a TPV cable it is a 700 R4. Also look at the shifter mechanism, if there is not a multi pin plug in bolted to the trans and just a regular old school lever like a t-350 that clues you also. I just got a wrecking yard 700 from a 92 chev van, I was suprised it wasn't a 4l60. Oh and it cost me around a hundred with a 12 month warranty, (replacement only) I took it to my trans guy, he pullled it apart, installed a corvette servo and a heavy duty b module (I think) and I'm into the trans for around three bills. Tough deal to beat considering I didn't have to mess around with towing, disposal, pissed off neighbors, titles, anyhow, just a thought.
One other thing, if you are considering a wrecking yard trans, look for one (If it's an older unit) with a painted torque converter. All reman, or replacement torque converters are painted, that means someone has already been into the trans. If it's bare, it is OEM.