I got my aluminum from a local radiator shop for $300. It's the same one Summit has. Direct fit in stock locations, has a drain petcock, outlets are in the original locations. It looks sweet and I never get above 180*. I also have no shround and run a clutch fan. Northern radiator

 

The top two maximum-cooling alum rads that drop into a 1965 Mustang are:

Griffin GRI-7-565BC-CAX

Fluidyne FLD-FHP30A-64MU

Personally I'd go with the Fluidyne because of the price. Also, the Griffin has no fan mounting brackets/flanges.

 

On the fluidyne radiator you have linked, either the description is wrong, or it's for a 67 & up. 26" is too wide for a '64-'66. I'd call first to insure that is the right radiator.
Stock the radiator is aproximately 21" tall, and 19" wide on the first generation Mustang.

If you have A/C you might be able to squeeze in as wide as 22" by modifying the battery tray, and off setting the raditor slightly to the passenger side. Otherwise 21" wide will fit (tightly). Or you can change the top A/C line that goes through the radiator support to move the it closer to the drivers side.
Without A/C you can go wider than that, by triming up the opening and fabricating new mount points.

 

That 26" wide description is a misprint by Summit. It's definitely for a 65-66. It's the exact same one Slickman dropped into his 65. We had a discussion about it.

 

i have the griffin and its awsome, drain plug and looks good. and was narrow enough to add an elec fan too

 

thanks for the tips
ill be buying one soon....ill post some pictures of my engine later this week