HP2 does not mean it's a six pack motor. Some say it means it was built on the second shift.
"The number 2, which you may find after the HP, (or in the case of non HP blocks, you may find just a "2" by itself, usually in the lower right hand corner of the ID pad) refers to the shift during which the engine was assembled. In running a factory, one 24 hour day can be divided into three 8 hour shifts. The first shift was considered a "1" however to save time, Chrysler did not stamp a "1", they just left it blank. So an HP2 engine, only means that the engine happened to be assembled on the second shift. There is no advantage to an HP2 block over an HP."