I do believe it is 357.

with a 4.000-4.060 bore and 3.850 stroke it's 393
with a 4.030-4.060 bore and a 4.000 stroke it's a 408
with a 4.030-4.060 bore and a 4.170 stroke it's a 427

the more metal you leave the cooler it will run and be more endurable it will be, so be conservative.