I don't think you need to have a roller cam to get it to fit. Your intake and oil pan and all the accessories should fit on the 79 motor but the firing order might be different.
But if you just want to know if it will fit ,, Then yes it will fit but you will need to take a lot of stuff off the mustang motor and use them on the 79 engine. But you can use the motor as it is. Use your oil pan and all the accessories off the mustang motor.
The blocks are not the same inside but they interchange.
never mind I just reread your post i thought you wanted to put the whole engine in
opps