I can't say for sure based on those pics, but if the shortblock is good, yeah. I'd inspect it closely to be sure. Any coolant or metal shavings in the oil?
Were it me, I'd replace them with PI heads/cams and a matching intake, while you're already doing the work...
This is just my opinion based upon my experience working on cars in home DIY garage (not a professional shop with a lift). To date I have done (4) motor swaps in my driveway using nothing but hand tools and a cheap harbor freight engine crane and engine stand. So I'm speaking from real experience and not just parroting someone else's forum post.
^^^This is the exact reason why I would pull the entire motor rather than attempt an "in vehicle" head repair. The motor is not so hard to pull in the Mustang. BUT once on the engine stand the access is soooooooooo much easier. Plus having the motor on the engine stand greatly increases the options available to react to any unexpected problems encountered.
I would also be concerned about the over all status of the block itself. IMO the amount of rust in the coolant jacket should not be over looked. The best solution is to have the block hot tanked and rifle brushed. (can you say engine stand options?). IF you don't clean out the coolant passages this creates the possibility of of having a newly reworked motor overheating. In fact, is it possible that someone has put some "stop leak" into the coolant jacket in an vain attempt to stop the leaks? If so this creates a whole new problem of it's own.
Another thing to consider is at the current time, do you have ANY idea about the bottom end of this block? Oil pick up? Bearings? Status of the oil pump? All things easy to do while a motor is on an engine stand.
Let me ask you about your experience. Are you able to determine IF the block deck is square? Are you positive that the block has not been warped by overheating? Unless the answer is yes IMO this is the best reason why the average DIY'er should do these sort of repairs by swapping whole motors.
Ho does make some very good points. If you want the engine to run for years to come, it would be worth the extra work/expense. It'd be a damn shame for the shortblock to let go after you do all this over something you would have seen on a stand.