My question is basically what is the difference? I pulled my 300 out and have a 351 I am rebuilding to put in it and have no idea which fan shroud to look for. I have the 2 row radiator.

 

Super cooled trucks had a 7 vs a 5 blade fan, an external oil cooler, and I believe a quad core radiator.

Adrianspeeder

 

IIRC trucks with the HD cooling also have a deeper fan shroud which does a better job of ducting air through the radiator.
The ports on 351 and the 300 radiators are opposite hand.
You'll need to address that issue as well.

 

Yeah I bought a new radiator and meant to get the fan shroud from the donor ruk but I forgot. I ought the biggest radiator option aailale fro Rock Auto and was just a little confused as to weher or not that was considered Standard or HD cooling.

Wow I'm feeling a litte thick skulled right now. I went back through my reciepts to get you a link to show which radator I had and right therei sys with hd cooling. Now to find a shroud or at leat te dimensions so I can go to te junkyards. Thanks for making me use y noggin.