if your still intrested, check out Fletchs carburated 5.0 mustang site he has an article in his tech section
Building a better boss
the machining is pretty straight forward any good engine shop can do it
manifold isn't cheap even a used one.
Pistons have to be changed due to the cantered valve angles and use the 289 rod 5.1555 not the 302 rod which will push the piston out the top of the block. unless you can find some that suit the 302 rod
its all there in the article
you have to admit the old windsor looks pretty hot with a set of cleveland heads sitting on it!