At the crank maybe.

My 96 GT final engine configuration 2v break down,.

96 4.6 stock short block
99 PI heads, shaved .027 and hand ported by me. I pocketed them and unshrouded the intake ports in the combustion chambers, exhaust ports were just polished. Cams were stock 2002 GT PI cams.
PI intake from 2000 GT.
Ported and honed upper plenum from 2004 GT,.. EGR port was filled in and smoothed with the honing.
BBK 75mm TB. Upper plenum was port matched to the TB.
BBK CAI
Screamin Demon ignition modules, 10.5MM MSD wires, NGK TR6 plugs gapped at .46
BBK 1 5/8 long tube headers with 2.5" collectors
2.5" BBK off road H-pipe
Flowmaster short 2 chamber mufflers into dumps.

Custom dyno tune performed by Brian of EFI-Unlimited,.. he was with James at RaceRelated at the time if this gives you an idea of long ago this was.

T45 tranny with 4.10 rear rear.

Originally made 269hp 293 trq before the head porting. Picked up 23hp after porting and made 292hp and 298 trq.

Thats a 4.6 pushing almost 11:1 cr with just about every possible mod you can do short of using aftermarket cams. With cams its doubtful the motor would have made more then 320 to the wheels. So I find it very difficult to envision a carb'd 4.6 with out headers making 290 to the wheels. They dont,.. they make 215 - 225 to the wheels with stock manifold. With out headers and every bolt on they still rarely exceed 250 rwhp. I cant see a carb conversion with timing locked at 19 deg picking up 50 hp on a 4.6. You can school me on the 5.0 motors. I'll be the first one to admit I dont know all the tricks. But I've done enough 4.6 engines on my own to feel confident and say that they did not put down those numbers as advertised.

Not trying to discredit you John. Not in anyway at all. But a 4.6 making 380 with stock cams just isnt going to happen. Not with 2v heads. I ported the piss out of my heads,. as good or better then anything you'd get from the big name shops, plus they had been shaved and I only picked up 23 hp with stock cams.

The the LSx with carb is apples and oranges to a 2v 4.6. LS1 heads flow almost as good as 4v B heads. The stock LS1 intakes are notorious for restricting HP. Its one of the 'manditory' mods on those motors like changing the MAF, TB and intake on a 5.0. For them going to the Fast intake or similar is an expected mod. I could see a Vic Jr and 750 carb on an LS1 making 80 hp or very close to it. Thats reasonable. They commonly pick up 40 - 50 HP with the Fast intake. But for a carb'd 2v 4.6 to make 100 more HP then a comparable EFI car? I dont see it.

Hurst