Just to recap...
I have a 1999 996 and sold the motor to fund a newer 999 motor, which I had ported, and installed S cams and 749 54mm Throttle Bodies and Wiseco 13.x:1 compression slugs. Can't remember the exact CR, but I'll measure it anyway once I've blueprinted the bottom end of the motor and rebuilt it.
Anyway, so the basic project is fitting the 999 motor with the shower TBs into the 996 frame (the non-Kyalami, standard 996 frame with the high V cross-brace in front of the vertical cylinder).
The issue is that there's no easy way to fit the 749/999 TBs into this frame, because of that cross-brace.
I waited 4 years before finally deciding to simply grind the cross brace out of the frame and weld a new, lower brace in under the 749 TBs and new 749 airbox bottom piece.
The second problem is the airbox itself....the 996 box does not fit the 749/999 TBs, nor does the 749/999 airbox fit the 996 frame. What to do? Simple, really....use the bottom of the 749/999 airbox to fit the TBs, and then gut the bottom of the stock 996/916/748 airbox out so that it forms the top part of a new "hybrid" airbox, which only requires a simple joining of the two pieces with fiberglass. Problem solved!
So, I went ahead and ground out the cross frame from the frame. (I'll weld a new brace in later, once the new airbox is built.)
Then, I trimmed the airboxes (using the bottom half of the 999/749 airbox and the top part of the stock 996/748/916 airbox, from which I gutted the bottom out)
Here you see the marking tape I used for the rough cut on the bottom half of the 999 airbox...and the gap that needs to be fiberglassed in to connect the stock 996 airbox above it...
Test fit the showers and stacks....
Finally, test fit the tank to ensure no problem with the showers sticking up (no problem found!)
Added some temporary fiberglass strips to join the two halves and hold them steady so that I can remove the new airbox and fill in the gaps properly and permanently, with fiberglass...(already dry and removed here...)
Next step...ordered fresh fiberglass and epoxy resin and some bagging supplies to join the two halves permanently.
Also ordering some stainless steel to make the new exhaust headers to fit the 999 manifolds to the 996 SilMoto Ti 54mm system that I have.