What do you think about this statement.........

Lol, metric bolts ...we're in the USA. HA HA HA! True enough but it is a world market out there. New design heavy duty engines designed in the good 'ol US of A are designed/engineered with metric fasteners for 3 to 4 decades now. Get with the times. The General, Ford and Mopar engine displacements are in metric and have been for years now.
For those that complain about people using Chev roller rockers on a Magnum, check the cost of Mopar rockers. You insist on Mopar parts you better be prepared to bend over. 1.7:1 Chev or Ford roller rockers are less expensive for a bit more lift. The issue is drilling and taping the bolt holes from 8mm to 7/16UNC for the studs to mount them.
It comes down to parts availability and fitment with cost in mind. If it works, have at it.