Radiator, doesn't look right

[AirSpeed]

Yesterday I noticed the radiator in my 72 GMC 4X4 was leaking, while trying to find the leak I noticed the rad doesn't fill up the top and bottom mounts, theres a 3/4" gap in the rubber cushions fitted in the mounts. I looked at my 69 and it's radiator fills the mounts. I also noticed the bottom of the shroud has a 3/4" gap at the bottom. Then I noticed the PO had cut a four inch piece of the bottom half of the shroud where it wraps around the fan. I think I have the wrong radiator and that's why it doesn't fill the mounts and the gaps and cut shroud. Did GM use different rads for my truck or did someone use the wrong one? By the way, I still can't find the leak! Any tricks finding a hidden leak? I have two extra radiators but a squirrel filled them with acorns and I can't get them all out! I tried for an hour, I got most out but can still hear several bouncing around that refuse to come out! The same squirrel also filled my MIG with acorns, I may find out what squirrel tastes like if he does it again.
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