No, it's not a HO. Is it a roller cam motor? Maybe. When Ford started making roller cam blocks, they were for Mustangs only, starting for the '85's. As time went on, Ford switched to only rollercam blocks around '87. However, a lot of these rollercam blocks had flat tappet cams. As a result, the bosses that hold down the spyders, will have to be drilled and tappeted.
There is a way to tell the roller blocks from the non-roller blocks. I forget exactly what it is, but it was by the starter, a casting # or something. But I will tell you that if you have 3 X's on the right side of the block above the tappets for cyl #'s 2 & 3 , it's a roller block.
If your son's motor has the cast nipples where the spyder would normally be blted to on a regular motor, these can be drilled and tapped for the spyders. also these blocks have the taller lifter bores for the roller tappets.
I had a guy at a swap meet who was going to give me a 302 truck motor like this to get rid of it. He didn't realize that it could be converted. I didn't take it, I didn't want to mess up my friends new Explorer!