The stock rockers are junk anyway. The factory ratios are not always accurate, and they can flex at high rpm's. A stud is always stronger than a bolt too. Not to mention the friction losses from a roller rocker. The pusrods you need are 6.7 inches in length too.
Also, With the stud mount roller rockers your stock valve covers will not fit. So after you spend the 100+ bucks on the new fancy Motorsport valve covers and bolt those on you will find out your upper intake won't fit anymore either due to the taller valve covers. The 3/8" intake spacer should work. If you use a 1" spacer I hope you have some pennies saved for a new cowl hood.
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1988 Mustang GT
12.0 @ 122
1992 BadAzz Wrangler
1993 Explorer