All the Pantera setups from Wilkinson I've seen used stagger-jetted 50 DCOE Webers, except for Forest Goodhart's rig that used two 454 GM TBI injector bodies. TBIs will run in any orientation but need a 12-15 psi fuel pump and some sort of controller. A stock Ford or GM TBI fuel pump will run inside a Pantera fuel tank without cutting the tank. Maybe the Dellortos were from Magnussen for GMs? 40mm throttle bores seem really small for a blown 350 ci engine (as do the 50mm Webers).
In a street-blower comparo' dyno run by HRM decades ago, the dual-Magnussen produced 7 psi max. The assembly (less intake) weighed 74 lbs with Webers on my scales. Wilkinson's special Pantera intake for the necessary reversed blowers used 2V cylinder heads, not 4V. There were two long aluminum shear- bolts holding the blower cases to the modified intake, in place of a burst panel used nowadays to prevent backfire damage to roots-type blowers.
Some higher rpm problems reportedly occurred with the rear Gilmer belt alignment between the reversed blower snouts and the end of the jackshaft or idler pulley (curable), and you need to modify the Cleveland's PCV system- or when boost goes positive, the rear window may get covered in engine oil from crankcase blow-by past the front main seal being carried by normal air flow up and out the rear opening over the deck. But everything fits under a stock engine screen.