Lets get into some specifics here .

1. Whats it going in ?
2. Pump gas motor or high compression motor ?
3. What about the rest of your combo , Cylinder heads , intake , cam, ect, ect.
4. Ultimatley , what are you trying to acheive , Cruiser or a racer . You cant have both .

-beerjet-

XMH 278 cam I assume 

-beerjet-

I realize forged is the way to go . But it is more money . He has a freshly turned crank and rods std/std . He also has a fresh set of closed chamber , large oval port heads and a roller cam as I mentioned above . The way I see it , he should run the fresh cast crank and stock rods with some good bolt . Reassemble and enjoy . I dont see those heads and cam really pushing a stock rotating assembly beyond it's limits . Save the coin and put it in your tanks . Thats my

Believe me , forged is the way but with the turbo 400 trans , I dont think you need it . Put the money in some good pistons and someone to put it together for you correctly .

-beerjet-

are you going to balance the motor ? if your going back stock with stock weight pistons and rods etc go with the cast crank if not , Got a couple of BBC steel cranks on the shelf if ya need one  Tom

Regardless of your combination,   You should balance your rotating/reciprocating weights.
Just my thoughts.

Cant disagree Doc ,but a balance isn't always in evreyones "grasp"  Tom