My thoughts on this, I ran a tall deck last motor a few things to remember, longer rod which I dont like just more chance for it to break. 2nd thing more weight. I wont run another tall deck unless I go with 600in or bigger and sure wouldnt do it with a 496ci motor. If you plan on never going bigger then 598 then use the short deck. I am also putting together a 496 for a back up motor I am just using the stock block for it 4 bolt main though.
DON'T I REPEAT DONT buy anything from Dynoflo you are wasting a lot of money.