Never documented this. In 1966 Olds didn't make a shroud that covered the entire width of the big car radiators. In short they used one shroud for both the A-Bodies (Cutlass/442) and big cars with about 30% of the big car radiators left out of the shroud.

5-10 years ago I modified my '66 Olds shrouds with additional material from a later 60's Toro shroud to cover the full width of the '66 big cars for better cooling. It's worked pretty well over all so here are some shots which show what to do. You have to use the '66 original shrouds to be able to bolt them into the factory mount points, but _what_ you bolt in can have extra material to cover the whole radiator, like so:

Front View

Sure you can pay big $$ to have a custom shroud made, but why not try a cheap ziptie first?

The extra material on the driver's side in my case came from later Toro shrouds on the theory that they'd have similar height and I could cut the width to fit. That worked. No reason you can't pull from other GM brands for a similar shaped part if you can't find a late 60's Toro shroud....

Rear View

Ziptie some extra width on the driver's side of your '65-'66 big car shroud for better cooling.

Hope this helps some of you. Usually this time of year, some of us get focused on better cooling....

Cheers
Chris

 

Good one. I thought of doing the same.