what flex plate are you running with your 351W AOD ? i am tring to do the swap and i am have trouble geting it bolted up right. the flex plate and torque converter are pushing each other.
Make sure the torque convertor is engaged all the way. You have to push and turn over and over till it finally clunks in all the way. I don't know how many clunks it takes for a AOD, but I bet at least 3. When it's right, you should have to actually pull the torque convertor forward about 1/2 inch so you can start the nuts or bolts on the torque convertor.
Yes, AOD uses the same flexplate as the C4, you'll need the 168 tooth (or whichever was the biggest one they made). Look for that flexplate for the 351/C4 combo or a pre-81 302/C4 combo, 302's had the same balance as the 351 until '81. Seem to remember hearing the 351 Clevelands were the same as well.