All BBC rods for low deck motors are the same length. 396/402/427/454 ...all use the same rod length. The LS6 / LS7/ L88 rods were beefier and had bigger rod bolts but the lenth is the same.
GM kept that same lenght rod by moving the pins around in the pistons to achieve proper deck clearance in the blocks. All the blocks are the same height also with of course the the exception of the TRUCK and later day 572 engines.
I cannot recall the lenght but any source that quotes a lenght for a BBC rod in a passenger car is giving you the correct length for your 427 rod.