Go to Grannysspeedshop.com and check out the 5.0 swaps. That 5 litre looks kinda small in the engine bay of a 2nd gen RX-7. I had a second gen with a worn out rotary engine & wanted to do this as an entertaining project, but didn't have the money at the time.
Uniqueness lost. Yes. Easy to let go when you're looking at a $1200 engine re-build versus buying a banged up $500 Mustang as a donor. A few years before my brother had an old Capris 5.0 HO with a bad steering rack that got rear-ended. I woulda given my right arm for that engine!