I have a 1987 mustang 5.0 with 119,000 miles. I have basic bolt ons like a cam, and a full exhaust. Well, i would like my next upgrade to be heads. If i put on heads that are good for like 50+ hp and a few other things with stock internals, will this be safe? i dont know where that point is to start uprading the internals. Any input would be helpful, thanks alot guys.