I bought a new 1987 f-150 xlt lariat 351 HO. I still have it and drive it regularly. I pulled the engine and disassembled it and the block and heads are no different from a regular 351. It had 4barrel intake with holly carb, single exhaust C6 transmission. As to cam I could not tell the difference from a average 351. The increase from 160 HP to 210 was mostly from 4 barrel carb although there may have been a small cam difference. Some have suggested it used a marine cam. The HO engine was discontinued about the middle of the 1987 run. All after that they were the EFI engines. I replace the engine with a 1969 351. These engine were different than the later engines .More meat in the lower end and larger intake ports not much difference in exhausts ports. Built this engine using the 4 barrel manifold a mild performance cam. You can hear the cam but it idles really well. This engine is very strong. You have to feather the accelerator on rainy days. Bottom line there is no factory installed 351 Ho engine in a f-150 after 1987 period

 

answered in post 2 ,

 

4bbl Holley 600 carburetor was the difference
That increased the HP from 150 to 210

 

good point, didn't shelby prove that back with the K code 289? ford 's K used a cast iron intake with a autolight, 271 hp, shelby used a self branded dual plane with a holly, 306 hp

 

Shelby also mounted that carb on a high rise aluminum dual plane intake. Hardly the same as the Ford iron intake. Ford came out with the Shelby version in 69 as their C9OX intake. and they used Tri-Y headers. So it wasn't all the carb change.

 

shelby did do a lot,came up with a lot of great working items, yet this is the intake i'm referring to that is on the 66 306 hp k code that i have, along with the 650 single feed holly .

 

baddad457 is this the highrise you spoke about?