The non HO intake has a smaller throttle body opening too. My friend has 3 complete SO engines out of his thunderbirds. They look like 55mm or smaller.
I did a search and found a site that explains converting cougars to HO. They were saying that there isn't much diffrence, the casting is a little different and the inlet tract is smaller. Which explains why when I looked at the TB I though it looked really small compared to what I remember. Also said the lowers were the same.
So what I might do then, since the upper I have will suck A**, is go ahead with the truck intake since I have the fabricating done for the Mass Air until I can get the larger TB and Egr and work ont he upper and lower. There is plenty of material to make the opening bigger on the upper.