I knew the hr article would come up. Here is a random sampler of what they found. The differences are so little it’s unlikely to be noticed driving. The peak numbers are intriguing to look at, but who knows why those are what they are when the averages look like this. Finding a deal on a manifold would be a way to free up budget for other things than to get caught up in absolutes like “it has to be this one, can’t be this one.” Likewise hood clearance is a crucial factor. There are inches of difference between some of those manifolds.

Average 2,500-4,500: 429 lb-ft, 289 hp
Average 4,500-6,000: 419 lb-ft, 417 hp
Average 2,500-6,000: 424 lb-ft, 344 hp

Average 2,500-4,500: 414 lb-ft, 280 hp
Average 4,500-6,000: 432 lb-ft, 430 hp
Average 2,500-6,000: 421 lb-ft, 344 hp

Average 2,500-4,500: 427 lb-ft, 288 hp
Average 4,500-6,000: 415 lb-ft, 413 hp
Average 2,500-6,000: 422 lb-ft, 341 hp

Average 2,500-4,500: 421 lb-ft, 284 hp
Average 4,500-6,000: 430 lb-ft, 427 hp
Average 2,500-6,000: 424 lb-ft, 345 hp

Average 2,500-4,500: 424 lb-ft, 287 hp
Average 4,500-6,000: 428 lb-ft, 426 hp
Average 2,500-6,000: 425 lb-ft, 346 hp

Average 2,500-4,500: 423 lb-ft, 286 hp
Average 4,500-6,000: 435 lb-ft, 433 hp
Average 2,500-6,000: 427 lb-ft, 348 hp

Random heights

front 311/42, rear 451/48
front 431/44, rear 531/44
front 311/44, rear 411/48
front 331/48, rear 411/44
front 351/48, rear 411/42
front 411/42, rear 511/42
front 351/48, rear 411/42