I'm trying to see if its worth swapping my speed density to a mass air sensor. My 86 GT is stock but I'm planning on getting some GT40 heads and intake later down the line. Is there any benefits if I do it now or should I just wait.
If you swap the cam then consider it. You’ll want to stay on top of vac leaks however as speed density is very sensitive to leaks. You might want to build a smoke machine and just periodically check.
Even if you swap the heads, the profile of the 86 cam stock cam is pretty decent. My old E cam mad a little more up top but it wasn't worth what it lost on the bottom and in the middle.
If you already have these GT40 heads then... ok. If not, don't buy any. Save your duckets for TFS Twisted Wedge, Long Tube headers, and whatever cam Ed Curtis tells you once you've filled out the cam profile sheet on his website.
There are folks here that are pretty good at cam selection too. It's mostly voodoo to me