Yep, there was never a delta-wing (Ramjet), or a STOVL (Thrust) version of the F-15, even just in planning. The closest is the F-15 Active, but even that doesn't look too much like Dirge.

 

Well, despite a detail here and there I still think the picture I posted at the start of this thread is probably the damnedest closest thing we'll have to a real Dirge. If you just imagine that jet in Dirges colors, you'll see it.

 

Well, it's the closest I could come up with for Ramjet. Considering that the Coneheads all were supposed to still have "cybertronian" alt. modes, similar wing shapes are about as close as you can get when trying to retool a toy that has to have two thrusters because they each form the robot heels.

 

I often look at Cyclonus as well and wonder.