Wow....this is all over the place. I have a 73 440 motor home short block in my car now. It came with big rods & the extra holes in the block deck, but I don't have the motor home heads, so they're blocked off & I've never had a leak or anything. The standard head gasket blocks those holes.

I've "heard" that the heads are just fine, that if you have the motor home heads you can drill two holes per cylinder in the deck and turn it into a motor home block (basically) to work with the heads, and that they cam with the big rods but lighter pistons so you could use a neutral balance harmonic balancer. I only bought the short block without the balancer and put on the offset weight balancer...but balanced my motor anyway, so might have wasted money hunting down a six pack balancer. I've also heard you can drill holes in standard head gaskets for the motor home head/block combo.