You are at a place with your Pantera where it is possible to do this now before you put the sheet metal skin back on.
Now you have the possibility of adding that structural reinforcement without it being intrusive into the cabin.
Granted there are going to be those people who find all that tubing desirable and an "industrial design/art statement", but here is your opportunity.

Also, even with a rear entry to the intake manifold, you still may not have enough room UNDER the rear deck lid?
How "worth it" is all of this re-engineering going to be? When it's done, is it still a "Pantera" or something else that just looks like a Pantera like some kind of a "NHRA Funny Car" with a plastic body that just lifts off?