I see ya got a GMC - might be retro, using the pre 55 setup - no U bolt in Chev TF rad mount hardware, nor a spring for that matter - for the Chevy TF years, there's mount pockets at the bottom of the core support, and the bolt goes thru those and some fat washers into the brackets that are riveted to the frame rails [not crossmember], and yes, an assembly manual is helpful, but I think there's not one for the GMC?

here's a pic of the Chevy core support , I think you need to be looking for GMC specific info .... American Classic lists GMC specific rad mount pads, like this

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics