On the intake testing I did on my 500HP 390 stroker engine, the Offy 2X4 finished 44th out of 50 intakes for average HP between 2800 and 6200 RPM, and 40th out of the 50 intakes for peak HP. It made about 463 peak HP on that engine, while the Blue Thunder 2X4 intake made 516 peak HP. The Offy intake was tested with Edelbrock carbs, not Holleys, but I doubt that the Holleys would have made a huge difference; maybe 10-15 HP. Also the distributor will not fit with the Holley carbs, unless you space the carbs way up so that the front float bowl of the front carb is above the distributor.
On my 425HP 428CJ, the Offy intake finished dead last out of 18 intakes in average torque and HP from 2500-5800 RPM.
There are lots of better intakes, both 4V and 8V, available for the FE.
1969 R Code Mach 1, Drag Week 2005 Winner BB/NA with 511" FE(10.60s @ 129), Drag Week 2007 Runner Up BB/PA with 490" Supercharged FE (9.35 @ 151)
1964 Ford Galaxie, Drag Week 2009 Winner Modified NA with 585" SOHC (9.50s @ 143)
1968 Shelby GT 500 Convertible, 492" 667 HP FE
2005 Ford GT, 2006 Drag Week Winner, 12.0 Daily Driver
1969 Ford Galaxie XL, 460 (Ho Hum....)