Just a point of reference regarding cost. My 700R4 recently died and sent it to local shop. I don't have the tools or the motivation to do it myself, you see. I asked about rebuilding the 700R4 vs a swap for a TH-350 or a TH-400. He told me the costs are about the same. The 700 would need to be rebuilt. The 350 and 400 would need some spacers and adapters as the splines don't match.
So the answer to your question is that it depends on how much you are willing to do or pay to get it done. Yes, its possible.
I have found that they now have a 350 (called a 350C) that has a lock-up torque converter. If you drive this on the freeway, I strongly suggest this upgrade.
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I ended up deciding to rebuild the 700R4 and add a few changes. I want a lock-up torque converter with a higher stall (about 1600-1800), new clutch packs from the 4L65E and kevlar bands.