Reply to "Transfer a race engine or build a new one ?"

My suggestion is to begin with a stock engine and a fully baffled 10-quart racing oil pan, and start your mods with the suspension. EVERY single parameter in the Pantera suspension is adjustable- thanks to designer Dallara, and doing this will allow you to progressively learn how the car handles at lower speeds. Learning to drive fast on-track in a mid-engine car is always a revelation to former drivers of front-engine machines. Things happen VERY quickly and it's best done NOT in a superfast car where mistakes can be covered up with power. Drivers don't learn anything that way.
I wrote a series of articles over the last 10 years for the POCA newsletter, in which the following are adjusted (front end):
toe-in
Ackermann toe-gain
caster
camber (two methods of adjustment lock)
bump-steer (two methods)
instant-center adjustment
swaybar sizing & tuning
shock tuning and corner-weight balancing
a-arm bushing materials
ball joints (I run racing Chrysler assemblies)
In the rear: bushings, toe-in and instant center adjustment, camber, ball joints, sway bar tuning and ZF set-up along with engine setback & lowering. Brakes should also be upgraded and a few aero mods should be considered.
I've not only done all this to our guinea-pig street Pantera L, it's currently 600 lbs lighter than stock and still runs A/C, wipers, both big bumpers, heater, a stereo/CD player & full interior. The car is stock-appearing with no gaudy wing. I estimate a full race-Pantera WITH a full roll cage could be built to 2400 lbs fueled & ready to run. Your stocker weighs around 3200 lbs w/no driver.
Stiffening up a race-Pantera chassis is best done by first seam-welding the entire body/monococque to replace the stock spot-welds, and correcting the usual rear suspension distortion BEFORE starting to try going fast.
Our POCA chapter has open track events where Mazda Miatas run with 500+ bhp Panteras & their mile-wide tires; the 'toy' Miatas blow their doors off in corners. No excuse for this except inexperience on-track, and poor suspension adjustments.
Nor-Cal Panteras has a track-only Pantera who's driver installed a 5-liter Ford out of his Mustang when he blew up a stroked 351-C. He found to his surprise that the 150 lbs lost and a few handling tweeks caused him to go faster than before. Today- 12 years later- he still hasn't bothered to rebuilt the stroker, and his 'little-motor' Pantera is faster every year! He regularly beats giant-power stroker-motor Panteras both in the corners and on the straights. IMHO, big-power engine building should be way down on your list of priorities.