Re: 428 engine?
Sorry to have to give you the news but it won't just sit right in... if in fact it is an FE engine. If you want it to fit in your mustang.....get your checkbook out. You'll have to cut and modify the shock towers and beef up the suspension, you may have to cut away the hump for the transmision to fit. You'll need a 9 inch rear, to handle the torque. The existing rear might hold up for a while...but that's a guessing game!!
If your turning the 65 into a race car...chopping it up won't be a factor but if you are planning on using for the srteet, or daily driver, that sure is a lot of work time and money.