I have a completely stock 1989 5.0 and I bought the 1.7 Ratio Pedestal Mount Roller Rocker Arms For Small Block Ford (79-95) #PFM-66878, will I need shims with these rockers or will they bolt no problems?
In theory they should work just fine on your application, however, Each engine can vary from the next so the only way to be 100% sure is to check the pattern that they leave on the valve spring. You can do this by putting a layer of assembly lube on the top of the valve stem that stick through the retainer. Bolt down the rocker arm and rotate the engine over. Take the rocker back off and look to see where the roller came into contact with the valve stem. It should be directly in the middle if it has the proper geometry. if it is offset, then you would need to look into shims to correct it.