I can see how there could be some confusion on the radiator applications for a 73-74. Technically, they're not a Ventura II because most (I think all) of them (71-72) came with a SBC and a little different core support. The support on a 73-74 can easily be modified to fit up to a 25x19, +/- an inch on the height, core radiator (even more if you open up the radiator opening). Any radiator from an X body application should work. If your going with a bigger core radiator, you'll also have to replace the rubber isolators at the top and the bottom in the core support and possibly find a different top plate (from a Nova specifically) that was meant for a wider 4 core radiator if that is what you are converting to width wise.
$400 is not a bad price for a drop in aluminum radiator and the Cold Case aluminum ones look just like a copper/brass radiator and are a nice piece. Hope my response isn't a "capt Obvious" read, just throwing it out just in case you didn't already know this or someone else was looking for some insight.
And by the way, nice car! Love the color!!!