[LockDoc]

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Here is a post by member "67 cst swb" about radiators:

To further clarify..

There are effectively 4 different radiators originally put in these 67-72 trucks, possibly more, but these are the main ones. there is 2, 3 or 4 row radiators (number of rows flowing from tank to tank)
There is one with a 26-3/8" wide core (measured from tank seam to tank seam) it is a 2 row radiator. This is typically a 6 cyl radiator

There are 3 with a 28-3/8" wide core (measured from tank seam to tank seam)

First is a 2 row. It is about 1-3/8" thick at the core. Typically a small V-8 non-AC radiator.

Second is a 3 row. It is about 2" thick at the core. Most common V-8 radiator or good upgrade for any non-AC small V-8 or 6 cyl.
All the radiators listed above have the 2-3/4" tank thickness (measured front to back), this is the portion that fits into the rubber saddle mount.

You can use any of the above mentioned "tanks" and have "re-cored" with the 28-3/8' by 2" replacement core. There used to be a 2-3/8" option for a replacement core. Not sure if its still out there.
The only variation of the above tanks is whether or not it has Automatic Transmission cooler/fittings in the passenger side tank.

Now... Lastly, there is the 4 row radiator.

It is the same 28-3/8" wide at the core, but it is 2-5/8" thick at the core.
It is also 3-1/2" thick tanks on it. If you upgrade to this radiator, you will need to change to the 4 row saddles and rubber mounts. People have put this radiator in the smaller (2 & 3 row) saddles, but this took some massaging and clearancing to work, as it is not intended for the smaller mounts.

All the above radiators are the same core height of 17" (16-7/8")
All the above radiators tank are the same height of 18-5/8" (difference being the thickness of either 2-3/4" (2 or 3 row) or 3-1/2" (4 row).
All above radiators were originally copper/brass construction.

Now, some people have purchased replacement radiators and they have been a aluminum core - plastic tank radiator with 2 rows. This works fine for most replacement application.

There are also numerous all aluminum radiators out there of various quality and construction. Depending on the tank seam type and construction. You may end up with an issue with it fitting into the saddle properly. The closer the aluminum radiator tanks resemble the OE tank style, the less problems you will have.

Hope this helps.
I know it a little too much info, but I just thought I would put it out here.

LockDoc