You lose a ton of compression with the 5.0 (E7) heads. 289 heads have a 54.5cc chamber, and I believe the 5.0 heads are 64cc. They also use a fulcrum type rocker arm setup, so different pushrods and rockers will have to be found. Flow differences between the two is a wash. No major advantages for either one. You will need to account for the difference in steam hole locations by drilling new holes in the head or deck of the block being used.
If you are looking for a way to increase the performance of your 289, this isn't it. If you are just looking to put a fuctional set of heads on your 289, it is possible, just be aware of the differences.
Good Luck!