Why bother with a 221 when the 250 is much easier to find, and would perform better anyway, the Dellow bellhousing isnt needed as there are C4 bellhousings to sixes out there, the factory used them quite often.
If your in the USA the a C4 will bolt straight to your 250 as it has the V8 bellhousing anyway.
The 221 whilst a good engine isnt worth the effort to find in my view, the rod ratio on the 221 isnt too flash and the 250 is bigger, the maximum airflow is limited by the head and if your using a 250-2v then it will fit either block, the 250ci with 2v head is a very nice combo, gives very good torque and will rev to about 4500rpm with stock cam, just a 350 or 500 two barrel will work great, tiny cam if you really want it.
The 250-2v has better low down torque than the 2 barrel 302.
A7M