JimB should have added "If you're lucky". Be aware that better quality transformers often have their laminations vacuum-impregnated with lacquer, which effectively welds them into a single block.
Vacuum impregnated means the laquer is drawn into the spaces. They are removeable. You just have to hit them harder.
E-shapes means you just use the E sides and not the I sides. I have seen some transfomers where all the E's were together and all of the I's were together and they were not interleaved. They were usually smaller transformers.
Looking at a commercial adapter, I;d say they were about 4" x 8" or so. Make judgements from there.