Not that you asked me, but I've got the same fans (or maybe mine are LS1's...only difference is the "shroud" is cut out in places for better airflow on mine, "other" style the shroud is "solid".) out of F-bodies.
Just worked out the fabrication details with my dad. The LS/LT1 fans are a bit narrower (maybe 1-2") than the "fullsize" gas radiator, and a few inches shorter than the radiator. They use goofy mounts (2 "hooks" on either side to hold it in place) and across the top, one "bar" that apparently fits in between cast "fingers" that protrude from the top.
Going to take two straps of metal from the factory truck shroud bolt holes in the upper radiator supports to the bottom of the core support, and angle iron across the bottom of the core support, which will bolt to the lower two stock shroud holes. All three pieces will be welded together obviously. Lower part of the shroud is perfectly flat, apparently the sides and upper portion of the shroud are all that kept it in the f-body.
Not sure what I'm going to do to hold the shroud "down", but I'll probably use round stock from one side to the other, weld nuts to the backside of the "straps" so as not to need a wrench on the backside. I could of course forego all this work, and just fix the fan in place, and unbolt the whole assembly when removal is necessary.
Would have loved to make it out of aluminum, but local store doesn't carry it, and it would be more expensive...not worth it for the weight penalty on a 5000lb vehicle. Cast iron to aluminum intake swap covered that anyways. /forums/images/graemlins/rotfl.gif
Probably more info than you needed to know, but as a "just in case" for anyone else considering the LT/LS1 fans. I think the windstars or other larger afn assembly would probably be easier to deal with. The LT/LS1 fans are designed to not use any bolts to secure them, and it makes mounting more difficult. I've got a fan with a broken mounting tab, so I know that it's possible, and drilling into it will only weaken the plastic.
Also, the fan wiring comes off the drivers side, which for us is a problem if you want as short wiring as possible. I think the plugs are interchangeable on the motors, which will allow you to route the wiring to the drivers side, and this is likely the easiest "problem" to work around.