Or would this one fit too http://cgi.ebay.com/New-PONTIAC-V8-...r_Truck_Parts_Accessories&hash=item5ade37d959
All Pontiac V8 distributors are interchangable so whatever you decide to go with will fit the engine. Don't want to get into advance curve discussion because every engine has it's own requirements.
No problem running the 485428 block to 650 HP if it checks out ok. That is the same block used for the `71-`72 455HO except for the HO being fitted with 4 bolt caps. The heads and cam package made most of the difference between the HO`s and the non.