Well sure, if you dont do something right than it wont be right, right?!
Trimming it is easy.
On electric fans, sure you can. But i nwouldnt buy all the garbage that is sold to bolt right on.
Since 81 fords have the same overall width radiator, but heights have changed.
From 81-07 they are all down flows.
Core width is around 30”, every era kind of increases in height around 3”.
Sooo, 81-97 has a core height of around 23.5, 99-03 26.5”, 03-07 around 29.5”.
The problem with most electric fan setups is they do a good job of blocking the core off, which is not good.
Also look at fan diameter, amp draw, cfm rating, etc.
So, with the Above numbers, a typical idi has a 30x 23.5” core.
Most fans youd prefer to use are 12-14”.
Proform make good normL enough fans that have a low amp draw, and move a good amount of air for their size.
I used to always make a 4 fan setup for whatever radiator, that makes it a nice open design, so not very restrictive when fans are off.
A typical idi core id use two 14” fans across bottom and two 10” fans on top.
It doesnt measure out right but fits perfect.
On a 99-03 core 2 14s and 2 12s.
On a 03-07 core 4 14s.
Im rusty on my numbers but on a 03-07, thats 6600 cfm @ 32 amp draw.
I think 2 14s and 2 10s might be 1200 cfm less.
I usually make the frame out of aluminum strap. It would bolt up exactly in place of shroud.
Wiring it is also where people get very confused.
You need two ways of turning it on.
Water temp and ac high side pressure.
Idis have hot thermostats, so youd want to find a setting thats around 10 degrees a above. I use little setrab temp switches. Very reliable.
Ac switch i usually have turn on around 250 psi and off around 175.
You can do that a few ways.
All these switches are just controlling ground inputs.
So, it is also super easy to add a over ride switch in cab to turn them on whenever you want.
So for some the question is what is enough cfm to work?
Anything around 5000 or more i have found is enough to mAintain normal high side ac pressure in the heat of summer.
So, if i can maintain a normL ac pressure at idle on a hot truck, with the basically no ducting these old trucks coolers have, then that is enough air blowing across your radiator as well.
But.
Clogged core, whether inside or out, and other variables effect that.
But, the last idi i had, it had a basic china aluminum 3 core radiator, 94-97 r134 condensor, 03-07 intercooler, and at idle with fans on nothing would get out of normal, and in central tx heat they would cycle off with the ac switch, which says it would drop the ac pressure below 175. I use a different tstat in the idi so my water temp usually ran 180s, but sitting idling for a bit would quickly cool below.
But.
A different fAn blade is like lots easier and works great.