Some clarifications...
The 440 rod is longer than the B wedge rods because of the deck height varience between B and RB.
The six pac rod as a unit is weaker. Only the rod beam section is stronger because it's thicker. Unfortunately the weakest point of any rod is the bolt bosses and the bolts themselves. Six pac rods use the same 5/16 bolts and nuts aas the LYs, but they are a lot heavier. So the small bolt has more weight to hold. So overall the LY rod is stronger.
In terms of this build - I'd get a set of B wedge rods and use available parts to rebuild it assuming the lifter bores are intact and the rest of the block isn't cracked.