How to position adjacent transformers so they don't interfere?
Toroids have very little magnetic leakage, so if you can find two of those, that would be ideal. There are many toroidal transformers for sale on eBay, give that a try. E-I laminants are pretty good also. Is this for a high-end audio amplifier? Magnetic flux dissipates inverse-square with distance, so even a few inches is good enough for most applications. If you can put them on opposite sides, even better. :)