I would go with Molnar or Scat myself. Pistons would befinately need to be ordered, large number of manufacturers to chose from there. Cost will be an issue. Molnar or Scat would probably finish the rod journals to the Mopar 2.123" diameter for you. Otherwise Chev 6.125" or 6.2" rods would need to be sourced. Of course stroke and rod length need to be nailed down before ordering the pistons. The 273 bore is an odd one in that it is larger than most in the 3.5" area but smaller than the 3.7" bunch. The thin wall casting will not allow boring that much out. A few of the V6 engines have pistons that would be close but are all 4 valve head designs. Their compression height is also pretty short with small diameter gudgeon pins.
