The correct diagnosis for fan circuit is a simple voltage test at the 3 wire connector behind the brake booster. [ on the firewall]
That is where you should have gone way before changing the blower and regulator. It is a simple 30 sec test that will test both the fan power feed and the CP output for the Regulator circuit. Don't go down to blower and stuff until you do the test up top. Specially on that chassis,,,
Three prong plug ...Red/Blk/Yl
Red + to Blk - , 12V
Yellow to Black , variable V. , 2-9 v , depending on the settin the CC panel.
Key ON.
If both test PASS , the problem is the reg..if Variable V does not, the CP is the problem.
You may want to use the Search Feature we have here on top of the page..all these primary test are explained in detail there several times over...and they will save you time and $$$$.

....and the Last thing you want on that Reg/Blower circuit is to protect it [ or should I say Not protect it ] with a 50 AMP fuse.....

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A Dalton