351w roller cam?
BE EXTREMELY CAREFULL IN DOING THIS!!!!!! Directly uder these holes lies cam bearings. Take the tap too far down and you will wipe out the bearings. I know this for a fact. My.....uh......friend....yeah that's it.....my friend did this and had to pull the block down to scratch to go back to the machine shop for new cam bearings. Luckily, I.....I mean my friend, had the motor on a stand and this was more of an inconvience than anything else.
Anyway, once you have your bolts tapped all you will need to do is either get all of the valvetrain from a 5.0 Mustang or order the equivalent from Summitt. You will need to source lifters, pushrods, the lifter guide bar, and *IMPORTANT* the correct bolts to hold down the lift bar. Use the same bolts that came from the factory for the hold down. Bolts that are too long will hit the cam bearings and you know the rest of the story.
Double check the pushrods needed for this. They might be different lengths than the 5.0.
Good luck. My conversion cost me a total of $52.00



