Is there any advantage to having an '86 engine?

[Hozer 88GTConv]

"...lack of valve eyebrows in the pistons limit the amount of valve lift that can be used.
The high swirl combustion chambers are useless for performance and essentially render the heads junk.
The intake manifold has tiny ports and a 58mm TB limits performance.
Replacement heads, intake and throttle body are the minimum changes just to bring this engine up to par with the 1987-or-later engines...."
Mustang Performance Handbook....
Sorry, but it seems that you are on the right track anyway...
Good Luck.