Keith, I agree that parts proliferation was the likely reason for the choices made.
The '65 chart reminds me that '65 was quite a revision from '64. All '64 GTOs got a tall radiator. But '65 GTOs got a short radiator unless they got AC.
Seems weird to me that they chose to have a Man Trans specific Rad without Trans Oil Cooler for the Tall Rad but not for the standard short Rad, the TT.
In '64, the Tripower got the HD tall Rad early year. In January, the '64 Tripower was downgraded from a standard 3.55 axle to a 3.23 axle. But it continued to get the HD Rad. I have contended this was an oversight. Sometime in March it appears that PMD wised up and the Tripower was downgraded to the same 2" thick tall Rad that the 4 bbl GTO was getting.
For '65, the only GTOs getting a Tall Rad seem to be the ones with AC. And in this case there were two versions, the Code TX (auto trans) and Code TV (man trans without Oil Cooler).
So even if proliferation was the argument, were there really fewer Man Trans Tripowers as compared to AC equipped Man Trans 326 A bodies and GTOs? I suspect they underestimated and if you check the '66 Charts, they may have corrected the misjudgment for '66.
As mentioned, the '64 GTOs only got the tall Rad. The late release Man Trans tall Rad codes were the Code 150 and the Code 159. Only the last 2 digits of the Code will appear on the '64 KC and Balt PHS docs.
By p/n, the Code 150 was p/n 3003450. It was the 2" thick Tall Rad without Trans Oil Cooler.
The Code 159 was p/n 3003459. It was the 2-5/8" thick Tall Rad without Trans Oil Cooler.
The Auto Trans Tall Rad was Code 157, p/n 3002157 for the 2".
And Code 158, p/n 3002158 for the Auto Trans 2-5/8" Tall Rad.
All early '64 GTOs got the Code 157 or Code 158 Rad. After the release of the Code 150 and Code 159, some Man Trans GTOs continued to get built with the Code 157 and Code 158 Rads.
And as I mentioned earlier, the Service Replacements were only listed with the Trans Oil Cooler.
I don't know when the Code 150 and Code 159 were released but they were not listed on the Rad Chart in the '64 Tempest Inspector's Guide that contained all Engineering Releases and Supersedures as of Dec 19, 1963.
After all this and taking another look at the '64 Inspector's Guide, I think I now understand what happened.
In '64, the Short 15.5" Rads were NOT used with AC or for any GTO. The only Man Trans A bodies that could have used a specific Man Trans Short Rad were the 326 builds without AC.
First I notice that there is an error in the Inspector's Guide for the Code 155 Rad. Code 153 was the 2" thick Short Rad that was standard for a 326 with auto trans. It included a Trans Oil Cooler.
The Code 155 was the 2" thick Short Rad that was standard for a 326 with man trans. It did not have a Trans Oil Cooler. But the application usage shown in the Inspector's Guide was the same as for the Code 153, in other words it showed the usage with Auto Trans when it should not have.
Meanwhile, the standard Rad for the 326 HO (4 bbl) was a 2" thick Short Rad, Code 156. It included a Trans Oil Cooler. The p/n was 3158956. It had tighter fin spacing than the Code 153/Code 155.
Turns out there was no equivalent 2" Short Rad released in '64 without Trans Oil Cooler for use with Man Trans.
And to round out the '64 applications, there was a Heavy Duty Cooling option for use with any 326. It was the Code 154. It was 2-5/8" thick and also included a Trans Oil Cooler. The p/n was 3158154 and same as with the Code 156, there was no equivalent for this Short Rad without Trans Oil Cooler for use with Man Trans.
So whether by oversight or a desire to avoid a proliferation of low volume components, it seems Pontiac only released Man Trans specific Rads for the 2" and 2-5/8" Tall Rads but only one of the two 2" Short Rads.
And they also did not release a Man Trans specific Rad for the 2-5/8" thick Short (15.5" tall) Rad. This was the '64 equivalent to the '65 Code TT.
The big change was to downgrade the GTO from the Tall Rads in '64 to the Short Rads in '65.
The use of the Short Rad for the GTO meant that there was no longer a need for a 2" thick Tall Rad which eliminated the need for a '65 equivalent for the '64 Code 157 and Code 150 2" thick Tall Rads.
With that exception, I think the same Rad choices carried over for '65 but because the GTO without AC now used the Short Rad, there was no Man Trans specific 2-5/8" thick Rad without Oil Cooler available for the Tripower, only the 4 bbl using the 2" Rad.
The only way to get a Tall Rad in a '65 GTO was to order AC. For a Tripower '65 GTO, I believe that meant the shortest rear gear you could get was the 3.23 when AC was optioned.
And with AC and Man Trans, you would have gotten the Code TV Rad without Trans Oil Cooler.
I realize Keith answered the question. But Keith knows I like to dig deeper and can't ever explain as succinctly as he can. Hence this long post.
